English version last updated on 28 June 2023. This page answers the most frequently asked questions about COVID-19 vaccines and vaccine safety. If the information you are looking for is not here, check out our related links on the right-hand side of the page.
There are several COVID-19 vaccines approved for use by WHO (given Emergency Use Listing) and from other stringent regulatory agencies (SRAs). The first mass vaccination programme started in early December 2020 and the number of vaccination doses administered globally is updated regularly on the WHO COVID-19 dashboard.
Different types of vaccines against COVID-19 have been developed, including:
For the latest information on vaccines, please visit the COVID-19 vaccines page.
For more information about all COVID-19 vaccines in development, see the COVID-19 vaccine tracker and landscape, which is regularly updated.
Watch the “Vaccines Explained” series for an explanation of the different types of COVID-19 vaccines.
The WHO EUL process determines whether a product (like a vaccine) can be recommended for use in an emergency situation based on all the available data on safety and efficacy and on its suitability in low- and middle-income countries. Vaccines are assessed to ensure they meet acceptable standards of quality, safety and efficacy by reviewing clinical trial data, manufacturing practices and quality control processes. The assessment weighs the threat posed by the emergency against the potential risks or benefits that would result from vaccine use. In line with their national regulations and legislation, countries have the autonomy to issue emergency use authorizations for any health product. Domestic emergency use authorizations are issued at the discretion of countries and are not subject to WHO approval.
On 5 May 2023, the WHO Director-General announced that COVID-19 is no longer a Public Health Emergency of International Concern. As a result, new COVID-19 vaccines are no longer eligible for an EUL. The EUL status of currently listed vaccines will be maintained for a limited period while the product transitions to prequalification (PQ) and if the product continues to be supplied to LMICs.
More information about the EUL procedure can be found on the WHO EUL webpage.
Getting vaccinated could save your life. COVID-19 vaccines have saved millions of lives since their introduction and provide strong protection against serious illness, hospitalization and death.
It is still possible to get COVID-19 and spread it to others after being vaccinated. Therefore, consider continuing to practice protective and preventive behaviours such as keeping a distance, wearing a mask in crowded and poorly ventilated spaces, practicing hand hygiene, respiratory etiquette (covering your mouth and nose with a bent elbow or a tissue when you cough or sneeze), getting vaccinated and staying up to date with booster doses. However, if you do get COVID-19 after vaccination, you are more likely to have mild or no symptoms than if you hadn’t been vaccinated.
Even if you have had COVID-19, WHO still recommends that you get vaccinated after infection because vaccination enhances your protection against severe outcomes of future COVID-19 infection, and you may be protected for longer. Furthermore, hybrid immunity resulting from vaccine and infection may provide superior protection against existing variants of concern.
To ensure optimal protection, is important to receive COVID-19 vaccine doses and boosters recommended to you by your health authority.
WHO’s Strategic Advisory Group of Expert’s on Immunization (SAGE) outlined three priority-use groups for COVID-19 vaccination: high, medium and low. In March 2023, SAGE updated its recommendations on primary series vaccination (two doses of any WHO EUL vaccine) as well as the need for booster doses for the current context, where many people already have had COVID-19. These recommendations are time-limited, only applying to the current epidemiological scenario; therefore, the booster recommendations are not currently annual recommendations.
The high-priority group are populations with the greatest risk of severe disease and death. Health workers are also considered a priority group due to their frequent interaction with patients, and particularly those who are at risk of severe disease. They include oldest and older adults with multiple significant comorbidities; younger adults with significant comorbidities (e.g., diabetes and heart disease); children aged 6 months and older with immunocompromising conditions (e.g., living with HIV and transplant recipients); and pregnant persons, as these populations are at the greatest risk of severe disease and death. In addition, health workers are a priority group due to their frequent interaction with patients.
The high-priority group should be prioritized for the primary series vaccines as well as first and additional booster doses. The additional boosters should be administered either 6 or 12 months (depending on your risk category) after the last dose, with the timeframe depending on factors such as age and immunocompromising conditions.
The medium-priority group includes healthy adults – usually under the age of 50–60 without comorbidities, and children and adolescents with comorbidities. SAGE recommends primary series and first booster doses for the medium-priority group. Although additional boosters are safe for this group, SAGE does not routinely recommend them, given the comparatively low public health returns.
The low-priority group includes healthy children and adolescents aged 6 months to 17 years. Primary and booster doses are safe and effective in children and adolescents. However, considering the low burden of disease, SAGE urges countries considering vaccination of this age group to base their decisions on contextual factors, such as the disease burden, cost-effectiveness, and other health or programmatic priorities and opportunity costs.
See here for SAGE’s latest recommendations on vaccination according to priority use group.
There are very few conditions that would exclude someone from being vaccinated, but you should NOT be vaccinated if:
COVID-19 vaccines are safe for people taking blood thinners, but you should inform the person administering the vaccine to you about any medication you are taking before you are given the vaccine.
In addition to the general recommendations above, each vaccine may have specific considerations for specific populations and health conditions. Talk to your healthcare provider for advice about your specific situation.
Yes. Even if you have already had COVID-19, you should be vaccinated according to your national recommendations. Although the protection that someone gains from having COVID-19 will vary greatly from person to person, current evidence suggests that hybrid immunity resulting from vaccine and infection may provide superior protection against existing variants of concern. When people are vaccinated after infection, they enhance their protection against the severe outcomes of future COVID-19 infections. Getting vaccinated after you have had COVID-19 means you are more likely to be protected for longer.
There is currently no evidence to determine the optimal time that you should wait to be vaccinated after having COVID-19. Persons with laboratory-confirmed COVID-19 infection can consider delaying vaccination in accordance with the recommendations of their national health authority. For more advice, consider discussing with your health care provider.
All vaccines approved by stringent regulatory agencies (SRAs) or with WHO Emergency Use Listing (EUL) are safe and effective at reducing the risk of severe disease and death due to COVID-19 infection.
Please remember that the benefits of COVID-19 vaccinations outweigh the risks of getting severely ill with COVID-19. If you are able to get vaccinated, do not delay it. Getting vaccinated could save your life.
Read more on different types of COVID-19 vaccines here.
For the latest information on vaccines, please visit the ‘What you need to know’ pages for AstraZeneca, Covaxin, Johnson and Johnson (J&J), Moderna, Novavax, Pfizer, Sinopharm and Sinovac.
There is evidence that the immunity you get after receiving a COVID-19 vaccine provides good protection against severe disease and death. Recent studies also show that even if someone has had COVID-19, vaccination adds additional protection, providing hybrid immunity. Therefore, it is important to get vaccinated, regardless of prior COVID-19 infection, especially for people from high-risk groups.
COVID-19 is a life-threatening disease that can have long-term consequences. COVID-19 vaccines that have Emergency Use Listing by WHO have been safely administered to billions of people. It is much safer to get vaccinated than it is to risk getting COVID-19 or its long-term consequences, like long COVID, the effects of which are still not yet well understood. Get vaccinated according to your country’s recommendations with the available vaccines and keep doing everything you can to protect yourself and others.
The COVID-19 vaccines with WHO EUL or approval from stringent regulatory authorities (SRAs) provide different levels of protection against infection, mild disease, severe disease, hospitalization and death, and are most effective against severe disease. Research is ongoing by thousands of scientists around the world to better understand how new virus mutations and variants affect the effectiveness of the different COVID-19 vaccines.
The current evidence shows that vaccines help prevent severe disease and death for high-priority groups (which includes oldest and older adults with multiple significant comorbidities; younger adults with significant comorbidities; children aged 6 months and older with immunocompromising conditions; healthcare workers; and pregnant persons) in the context of the Omicron variant. Though current vaccines are less effective at protecting against infection and mild disease than they were for earlier virus variants; if you do get ill after being vaccinated, your symptoms are more likely to be mild.
The Technical Advisory Group on SARS-CoV-2 Virus Evolution (TAG-VE) is a group of independent experts who regularly meet and continue to assess the available data on the transmissibility, clinical severity, and immune escape potential of variants, including the potential impact on diagnostics, therapeutics, and the effectiveness of vaccines in preventing infection and/or severe disease. Their recommendations are used to inform WHO on global, regional and national COVID-19 prevention and control strategies and are utilized by other WHO advisory groups.
WHO continues to recommend the use of all existing COVID-19 vaccines with WHO Emergency Use Listing (EUL) and bivalent vaccines with stringent regulatory authority (SRA) approval since they continue to protect individuals, particularly those at highest risk from severe illness and death.
Remember that while the COVID-19 vaccines with WHO EUL or approved from SRAs are incredibly effective at reducing your risk of developing serious illness and death, no vaccine is 100% effective. This makes it very important to consider continuing to practice public health and social measures, even after being up to date with the COVID-19 vaccines as recommended by your country’s health authority.
It is safe for you to receive a second primary, first booster, or any additional booster dose with a different COVID-19 vaccine than the one used for the previous dose(s), according to your country’s recommendations. Depending on the type of vaccine, using a different type of vaccine may even provide better protection than using the same type of vaccine.
If you’re offered a different type of vaccine, you can go ahead and get vaccinated. WHO considers two doses of any WHO EUL vaccine to be a complete primary series. See the full list of COVID-19 vaccines with WHO EUL here.
WHO’s Strategic Advisory Group of Experts on Immunization (SAGE) has published recommendations on approved vaccines for primary series vaccination and booster doses. You can find information on all the SAGE-recommended vaccines by visiting the COVID-19 vaccines page.
See here for the latest SAGE recommendations on which vaccines can be safely mixed and matched.
Like with any vaccine, some people will experience mild to moderate side effects after being vaccinated against COVID-19. This is a normal sign that the body is developing protection. Side effects to COVID-19 vaccines include fever, tiredness, headache, muscle ache, chills, diarrhoea and pain or redness at the injection site. Not everyone will experience side effects. Most side effects go away within a few days on their own. You can manage any side effects with rest, plenty of non-alcoholic liquids and taking medication to manage pain and fever, if needed.
More serious or long-lasting side effects to COVID-19 vaccines are possible but extremely rare. Vaccines are continually monitored for as long as they are in use to detect and respond to rare adverse events.
Read more:
Depending on your country, there may be a 10–15-minute waiting period to ensure that you do not experience any immediate side effects after vaccination.
The vaccine stimulates your immune system to protect you from the virus. This process can sometimes cause side effects like fever, chills or headache, but not everyone experiences side effects. The presence or magnitude of the reaction you may have after vaccination does not predict or reflect your immune response to the vaccine.
You do not need to have side effects to be protected.
If you are worried about your side effects, contact your healthcare provider and let them know about your recent vaccination. If you experience difficulty breathing, chest pain, confusion, loss of speech or mobility after your vaccination, contact your healthcare provider immediately.
Serious side effects due to COVID-19 vaccines are rare. Known possible severe side effects for each COVID-19 vaccine product with WHO Emergency Use Listing (EUL) are included under each vaccine’s product-by-product information section on WHO’s website.
In very rare cases, some people may experience an allergic reaction after being vaccinated against COVID-19. A severe allergic reaction – such as anaphylaxis – is a very rare side effect of any vaccine.
If you have a history of allergic reactions, talk to your healthcare provider before you get vaccinated. They will be able to give you advice. In some cases, precautions will need to be taken for people who have known allergies to previous doses of the vaccine or known components of the vaccine.
Healthcare workers administering COVID-19 vaccines are trained to recognize and treat serious allergic reactions. This is why people being vaccinated against COVID-19 will be asked to stay at the vaccination site for a period of time following their injection, to ensure that anyone experiencing an allergic reaction can receive prompt treatment.
Reports of adverse events following COVID-19 vaccination (including allergic reactions) are closely monitored by national authorities and international bodies, including WHO for the early detection of serious side effects.
As with any vaccine, it is essential to closely monitor the safety and effectiveness of COVID-19 vaccines. If a serious health problem is reported following vaccination, a thorough investigation should take place by the relevant health authorities in the country.
It is rare to find that serious health problems occurring following receipt of a vaccine are actually caused by the vaccine itself. Serious health problems following vaccination are most often found to be coincidental and entirely unrelated to vaccination. Sometimes they are related to how the vaccine has been stored, transported, or administered. Errors related to the delivery of the vaccine can be prevented by better training health workers and strengthening supply chains.
The safety of COVID-19 vaccines is a top priority for WHO.
Find out more about how the safety of Covid 19 vaccines is monitored.
Yes. Vaccines with WHO Emergency Use Listing (EUL) status or authorized by stringent regulatory authorities (SRAs) are most effective at reducing the risk of severe disease and death from COVID-19 infection.
While COVID-19 vaccines are highly effective against serious disease and death, no vaccine is 100% effective. As a result, vaccinated people can get infected and may fall ill with COVID-19 despite being up to date with their COVID-19 vaccines and any booster doses recommended for their priority-use group. This is known as a ‘breakthrough infection’ or ‘breakthrough case’. With more infectious virus variants, we are seeing more breakthrough infections and cases.
Breakthrough infections can happen with every vaccine and do not mean that the vaccine does not work. People who get COVID-19 after being vaccinated are much more likely to only experience mild symptoms as effectiveness against serious illness and death remains high. Vaccine effectiveness wanes over time, so make sure you are up to date with any necessary vaccinations including booster doses according to your country recommendations.
No. Even if you are vaccinated it is still possible to transmit the virus to others, including those who may be in danger of severe disease, hospitalization or death. It is important that those who have symptoms or a positive test result self-isolate until the infection has passed, regardless of their vaccination status.
No. Even after getting vaccinated, you should consider taking precautions to protect yourself and others against COVID-19.
COVID-19 vaccines are most effective against severe disease and death but have limited impact against reducing symptomatic illness and transmission. There is also a chance that you could pass the virus on to others who are not vaccinated. Some people have not been vaccinated against COVID-19, cannot be vaccinated, or do not develop full immunity in response to COVID-19 vaccines because of having a weakened immune system. Consider continuing the practice of protective behaviours to protect yourself and others.
The duration of a vaccine depends on the product and efficacy, as well as whether booster doses are received. There is increasing evidence that the effectiveness of COVID-19 vaccine against infection and mild symptoms as well as severe disease, albeit at a slower rate, wane over time. Although it should be noted that the approved COVID-19 vaccines provide a good level of protection against severe disease, hospitalization and death. A booster dose should be taken when offered, to strengthen protection against serious illness and death from COVID-19.
Immunity may reduce faster in people who are older or who have underlying medical conditions, or who have a high level of exposure to the virus, so those in high-risk groups should make sure that they are up to date with their recommended vaccination schedule.
As we learn more about COVID-19 and immunity, WHO will continue to update our guidance and recommendations.
WHO considers two or three doses of any WHO EUL vaccine to be a complete primary series. People with compromised immune systems don’t always develop maximum immunity against COVID-19 after one or two doses, so they may need an additional dose as part of the primary series. WHO recommends that those who are moderately or severely immunocompromised should be offered an additional dose of COVID-19 vaccine.
For Sinovac and Sinopharm, WHO recommends that countries consider offering a third dose of the vaccine to the vaccination schedule for those aged over 60 and those who are moderately or severely immunocompromised as an extension of the primary series.
An additional dose as part of the primary series is different from an additional booster dose. Different recommendations are in place for additional booster doses, please refer to the question: Who should get vaccinated against COVID-19?
A booster dose is an extra dose of vaccine administered to a vaccinated person that has completed a primary vaccination series (currently two doses of any WHO EUL COVID-19 vaccine depending on the vaccine and the population group).
WHO’s Strategic Advisory Group of Expert’s on Immunization (SAGE) has outlined recommendations for how many booster doses different groups should receive according to their risk. Some countries may make different recommendations depending on factors including national disease burden, cost-effectiveness and the epidemiological situation, so please check your national recommendations.
SAGE recommends the high-priority group should be prioritized for the primary series vaccines as well as first and additional booster doses. The additional booster should be administered either 6 or 12 months after the last dose, with the timeframe depending on factors such as age and immunocompromising conditions.
The high-priority group includes oldest and older adults with multiple significant comorbidities; younger adults with significant comorbidities (e.g., diabetes and heart disease); children aged 6 months and older with immunocompromising conditions (e.g., living with HIV and transplant recipients); and pregnant persons, as these populations are at the greatest risk of severe disease and death. In addition, health workers are a priority group due to their frequent interaction with patients.
The medium-priority group includes healthy adults – usually under the age of 50–60 – without comorbidities and children and adolescents with comorbidities. SAGE recommends primary series and first booster doses for the medium-priority group. Although additional boosters are safe for this group, SAGE does not routinely recommend them, given the comparatively low public health returns.
The low-priority group includes healthy children and adolescents aged 6 months to 17 years. Primary and booster doses are safe and effective in children and adolescents. However, considering the low burden of disease, SAGE urges countries considering vaccination of this age group to base their decisions on contextual factors, such as the disease burden, cost-effectiveness, and other health or programmatic priorities and opportunity costs.
Your need for an additional COVID-19 booster depends on your level of health risk to developing severe COVID-19. Additional booster doses are vaccine doses that are administered within a recommended time frame after the first booster dose is received.
According to the March 2023 WHO Strategic Advisory Group of Expert’s on Immunization (SAGE) recommendations, individuals who are at high-risk of developing severe COVID-19 – older adults; younger adults with significant comorbidities (e.g., diabetes and heart disease); people, including children aged 6 months and older with immunocompromising conditions (e.g., people living with HIV and transplant recipients); pregnant persons; and health workers due to their frequent interaction with patients – should continue to be prioritized and should be offered a booster 6 or 12 months after their last one. This is not a recommendation for annual boosters on a long-term basis, as there is insufficient data to support it.
At this time, WHO does not have enough data on whether bivalent COVID-19 vaccines are more effective than existing WHO Emergency Use Listing (EUL) COVID-19 vaccines. A Good Practice Statement was issued by WHO’s Strategic Advisory Group of Expert’s on Immunization (SAGE) on the use of variant-containing vaccines in October 2022.
As of March 2023, WHO SAGE recommends that countries can also consider using BA.5 bivalent mRNA vaccine for the primary series.
Do not delay getting your booster dose now in favour of getting a bivalent vaccine later. The best vaccine is the one that’s available to you first.
The term variant-containing vaccines indicates the fact that the vaccine was intended to help suppress a new variant of COVID-19 and does not mean that it contains the COVID-19 virus or any of its variants inside them.
No, the COVID-19 vaccine will not cause a positive test result in a COVID-19 PCR or antigen laboratory test. This is because the tests check for active disease and not whether an individual is immune. However, because the COVID-19 vaccine prompts an immune response, it may be possible to test positive in an antibody (serology) test that measures COVID-19 immunity in an individual.
Yes, although it is important to review the criteria of the countries you are travelling to or through prior to travel. WHO does not support using proof of vaccination as a requirement for international travel.
There is no known influence or interaction between antibiotics and COVID-19 vaccines. If you are prescribed antibiotics by a health professional before or after your vaccination, you should go ahead and take the full course. However, if you have a temperature over 38.5 ºC at the time of your vaccination appointment, you should reschedule for when you feel better.
There is no evidence that the safety or effectiveness of COVID-19 vaccines is affected by anything you eat or drink before or after getting vaccinated, including alcohol. However, drinking alcohol can add to the normal mild to moderate side effects that you might experience after vaccination, such as a headache and tiredness. Because of this, it is advisable to avoid drinking alcohol until any side effects following vaccination have passed.
Learn more about theside effects of COVID-19 vaccines.
Please keep in mind that drinking alcohol can increase your risk of other health problems.
Yes, although children and adolescents aged 6 months to 17 years are not considered a high-priority group for vaccination unless they are immunocompromised or with severe obesity or comorbidities putting them at higher risk of severe COVID-19. These groups should be offered the primary dose and one booster, though at a different dosage from adults. Significant comorbidities include diabetes, chronic lung diseases, heart, liver and kidney diseases.
Some of the vaccines that received EUL have also been licensed for administration as primary series vaccination or boosters to children from 6 months and adolescents. Considering the low burden of disease in healthy children, in March 2023, WHO’s Strategic Advisory Group of Expert’s on Immunization (SAGE) advised countries to base their decision on whether to vaccinate this group on contextual factors, such as the disease burden, cost effectiveness, and other health or programmatic priorities and opportunity costs.
Yes, you can get vaccinated if you are pregnant and it is strongly recommended. During pregnancy, you are at higher risk of serious illness caused by COVID-19. You are also at higher risk of delivering your baby prematurely if you contract COVID-19.
There is now a considerable body of evidence on the vaccination of pregnant persons, and no additional safety concerns have been identified. There is evidence to suggest that when a pregnant person is vaccinated, the antibodies created are passed from mother to child, which can help protect the baby for the first few months of life.
WHO’s Strategic Advisory Group of Expert’s on Immunization (SAGE) considers pregnant persons a high-priority-use group and recommends that they receive the full primary series (currently two doses of any WHO EUL vaccine), a booster dose and an additional booster dose if their last dose was given more than 6 months ago, ideally to be given by mid-second trimester.
Many WHO Emergency Use Listing (EUL) vaccines have been authorized to be used during pregnancy. The product-specific recommendations available on WHO’s website provide more information on each vaccine.
You can learn more about COVID-19 vaccines and pregnancy here.
Yes, you should get vaccinated if you are planning to get pregnant. There is no evidence that suggests the COVID-19 vaccines interfere with fertility. There is currently no biological evidence that antibodies from COVID-19 vaccination or vaccine ingredients could cause any problems with reproductive organs.
If you are breastfeeding, you should get vaccinated against COVID-19 with the available vaccine according to your national recommendations. None of the current COVID-19 vaccines have live virus in them. This means there is no risk of you transmitting COVID-19 to your baby through your breastmilk. In fact, the antibodies you get after vaccination may go through your breast milk and help to protect your baby.
You should get vaccinated if you are menstruating. If you have your period on the day of your vaccination appointment, you can go ahead and get vaccinated. Menstruation isn’t a medical reason to not get the COVID-19 vaccine. If you have concerns or questions about your periods, do not hesitate to speak with your health care provider.
There have been some reports of people experiencing disruption to their menstrual cycle after being vaccinated against COVID-19. There is not yet enough data available to know whether there is a connection between the vaccines and this disruption. Several large studies researching the impact of vaccines on menstrual cycles are ongoing. WHO will continue to monitor any new evidence regarding menstrual cycles. Information regarding these studies can be found here and here.
If you have concerns or questions about your periods, do not hesitate to speak with a health care provider.
WHO’s Global Advisory Committee on Vaccine Safety (GACVS) monitors how approved vaccines behave in the real world to identify any signals of adverse events following immunization. GACVS is an independent group of experts providing authoritative, scientific advice to WHO on vaccine safety issues of global or regional concern.
Unprecedented scientific collaborations allowed COVID-19 vaccine research, development, and authorizations to be completed in record time – to meet the urgent need for these vaccines while maintaining high safety standards.
The vaccines must be proven safe and effective in large Phase III clinical trials to prove that they meet internationally agreed benchmarks for safety and efficacy before they are introduced in national immunization campaigns.
Independent reviews of the efficacy and safety evidence are required by WHO for each vaccine candidate, including regulatory review and approval in the country where the vaccine is manufactured before WHO considers it for emergency use listing.
Please remember that the benefits of COVID-19 vaccinations outweigh the risks of getting ill with COVID-19. If you are able to get vaccinated, do not delay it unless advised to by your health care provider. Getting vaccinated could save your life.
Read more:
In rare situations where serious adverse reactions are suspected to be related to the vaccine itself, the vaccine may be temporarily suspended from use while the situation is assessed. Investigations will take place to determine what exactly caused the event and corrective measures will be put in place. WHO works closely with vaccine manufacturers, health officials, researchers and other partners to monitor any safety concerns and potential side effects.
Suspected safety events officially reported to WHO go through a series of rapid verification steps with the Global Advisory Committee on Vaccine Safety (GACVS). WHO then shares the results of these evaluations on its website and publishes the results of any assessments. WHO also coordinates with local, regional, and national health officials to investigate vaccine safety concerns and advise on next steps when requested.
Vaccine recalls or withdrawals due to safety issues are rare. Recalls are generally associated with problems identified during the monitoring of batches of vaccines through quality control systems, stability studies and reports from the field, including cold chain issues where some vaccines have not been stored at the right conditions and so are no longer safe or effective. In this case, people who have received a vaccine from that batch may need to be vaccinated again to ensure they are protected. This is why vaccines are so closely monitored: to ensure that any issues with their production, storage, transportation or use can be rapidly identified and resolved.
mRNA vaccines for COVID-19 are safe for those aged 6 months and older.
It’s important to note that prior to its use for COVID-19, mRNA vaccine technology had been studied for several decades, including in the contexts of Zika, rabies and influenza vaccines.
Prior to introduction, the COVID-19 mRNA vaccines were rigorously assessed for safety, as clinical trials demonstrated that mRNA vaccines produce an immune response that has high efficacy against disease.
Since November 2020, the COVID-19 mRNA vaccines with WHO Emergency Use Listing (EUL) have been administered millions of times, saving countless lives.
WHO is notified of safety signals through support to national monitoring systems, continually reviews incoming information, and keeps the public informed where there are changes to recommendations.
Find out more about the different types of COVID-19 vaccines and the safety of COVID-19 vaccines.
A very small number of cases of myocarditis and pericarditis – linked to the mRNA vaccines Moderna and Pfizer, and the protein-based Novavax vaccine – have been reported in vaccinees aged 12 years old and above.
Globally, mRNA vaccines such as Pfizer and Moderna have been used to protect millions of people against COVID-19. A significant amount of data is available from both clinical trials and country surveillance programmes on their efficacy and safety.
Men between 21–40 are more likely to develop post-COVID-19 myocarditis following administration of the Pfizer (more common) and Moderna vaccines and are more commonly observed after the second Pfizer dose.
Myocarditis is usually mild, responsive to treatment and much less serious than myocarditis associated with COVID-19 disease, or myocarditis from non-COVID causes. Early identification and fast treatment with medication and rest can help to avoid long-term heart damage and death. If you experience new and persisting chest pain, shortness of breath or have a racing or pounding heartbeat within a few days of vaccination, contact your doctor immediately. The benefits of these vaccines greatly outweigh the risk of myocarditis and pericarditis by preventing hospitalizations and deaths due to COVID-19.
WHO is notified of safety signals through support to national monitoring systems, and continually reviews incoming information. Based on the science and evidence reviewed and vetted with multiple experts from around the world, WHO has found the mRNA vaccines safe for use in the population. If that changes, WHO will update the public.
Please remember that the benefits of COVID-19 vaccinations outweigh the risks of getting ill with COVID-19. If you are able to get vaccinated, do not delay it unless advised to by your health care provider. Getting vaccinated could save your life.
For more information, please read the updated guidance from the COVID-19 subcommittee of the WHO’s Global Advisory Committee on Vaccine Safety (GACVS).
Click here for an infographic on myocarditis and pericarditis.
Globally, COVID-19 vaccines such as AstraZeneca and Johnson & Johnson/Janssen have been used to protect millions of people. Data are available from both clinical trials and preliminary data from country surveillance programmes on their efficacy and safety. Some mild to moderate side effects such as fever, muscle and head aches, soreness around the injection site and tiredness are expected to affect some people after vaccination. These are normal indications that the body is developing protection.
There have been reports of very rare but serious cases of blood clots accompanied by low platelet counts known as thrombosis with thrombocytopenia syndrome (TTS) occurring 3 to 30 days after vaccination with COVID-19 non-replicant adenovirus vector-based vaccines (such as the AstraZeneca and Janssen vaccines).
The cumulative incidence of TTS following vaccination with such vaccines ranges from 0.5 to 6.8 cases per 100 000 vaccinees. Incidence rates differ depending on the vaccine, age, sex, geographical distribution and interpretation of the case definition.
It is important to remember that blood clotting problems can be caused by many factors. Not all clots that occur after vaccination with Astra Zeneca or the Janssen vaccine will be due to TTS.
If you experience a new, severe, persistent headache, blurred vision, chest pain, severe abdominal pain, leg swelling or unusual skin bruising and shortness of breath 3–30 days following vaccination, contact your doctor immediately. WHO has published guidance for clinical case management of TTS following vaccination to support doctors in early identification and management of such cases.
The benefits of the COVID-19 Astra Zeneca and Janssen vaccines are far greater than the very small risk of TTS. WHO recommends that these vaccines continue to be used.
For more information, read the Statement of the COVID-19 subcommittee of WHO’s Global Advisory Committee on Vaccine Safety (GACVS) on safety signals related to the Johnson & Johnson/Janssen COVID-19 vaccine and the GACVS review of latest evidence of rare adverse blood coagulation events with AstraZeneca COVID-19 Vaccine.
There have been very rare reports of cases of Guillain-Barré syndrome occurring within 42 days of vaccination with the AstraZeneca and Janssen vaccines (adenovirus vector vaccines). Guillain-Barré syndrome is a rare condition in which a person’s immune system attacks the nerves, causing muscle weakness, tingling and/or loss of sensation in the arms and/or legs. Most people affected recover fully. Although these cases happened after vaccination, it is not yet possible to tell whether they were related to or caused by the vaccines or if they were coincidental. The benefits of vaccination against COVID-19 greatly outweigh any possible risk.
Globally, vaccines such as AstraZeneca and Johnson &Johnson/Janssen have been used to protect millions of people against COVID-19. Data are available from both clinical trials and preliminary data from country surveillance programmes on their efficacy and safety. Some mild to moderate side effects such as fever, muscle and headaches, soreness around the injection site and tiredness are expected to affect some people after vaccination. These are a normal indication that the body is developing protection.
As of the 27 June 2021, the European Medicines Agency had received reports of 227 cases of Guillain-Barré syndrome in the European Union following vaccination with AstraZeneca. Around 51.4 million doses of Vaxzevria (the brand of AstraZeneca produced in Europe) had been administered within the European Union by 20 June 2021. For the Janssen vaccine, the US Advisory Committee on Immunization Practices reported that 100 cases of Guillain-Barré syndrome had been reported through the Vaccine Adverse Events Reporting System in the United States of America (USA) as of 30 June 2021, with approximately 12.2 million doses of the Janssen vaccine administered. Outside of the European Union and the USA, cases of Guillain-Barré syndrome have also been reported; however, further investigation is needed to determine whether the rate has increased from usual levels.
Guillain-Barré syndrome has many causes, such as bacterial or viral infections, surgery or vaccine administration. It can also be caused by COVID-19. In 2011, it was estimated that the incidence of Guillain-Barré syndrome in Europe and Northern America was 0.8 to 1.9 cases out of every 100 000 people. It can affect people of all ages but is more common in adults and in males. Most people recover fully even from the most severe cases of Guillain-Barré syndrome; however, it is potentially life-threatening, and some people affected may need intensive care.
If you experience any of the following symptoms within 42 days of vaccination, contact your healthcare provider immediately:
The benefits of the COVID-19 Janssen and AstraZeneca vaccines are far greater than the very small risk of developing Guillain-Barré syndrome. COVID-19 disease can also cause Guillain-Barré syndrome. WHO recommends that these vaccines continue to be used.
For more information, read the Statement of the COVID-19 subcommittee of the WHO Global Advisory Committee on Vaccine Safety (GACVS) COVID-19 subcommittee on reports of Guillain-Barré.
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