This article is part of a series of explainers on vaccine development and distribution. Learn more about vaccines – from how they work and how they’re made to ensuring safety and equitable access – in WHO’s Vaccines Explained series.
Countries around the world are rolling out COVID-19 vaccines, and a key topic of interest is their safety. Vaccine safety is one of WHO’s highest priorities, and we’re working closely with national authorities to develop and implement standards to ensure that COVID-19 vaccines are safe and effective.
Ensuring safety
Billions of people have been safely vaccinated against COVID-19. All of the approved COVID-19 vaccines have been carefully tested and continue to be monitored.
Like all vaccines, COVID-19 vaccines go through a rigorous, multi-stage testing process, including large clinical trials that involve tens of thousands of people. These trials are specifically designed to identify any safety concerns.
An external panel of experts convened by WHO analyses the results from clinical trials and recommends whether and how the vaccines should be used. Officials in individual countries decide whether to approve the vaccines for national use and develop policies for how to use the vaccines based on WHO recommendations.
After a COVID-19 vaccine is introduced, WHO supports work with vaccine manufacturers, health officials in each country and other partners to monitor for any safety concerns on an ongoing basis.
New vaccine technology
Some COVID-19 vaccines have been developed with an approach that uses messenger RNA (mRNA). The mRNA vaccine technology has been studied for over a decade, including in the development of vaccines for Zika, rabies and influenza.
These mRNA vaccines have been rigorously assessed for safety, and clinical trials have shown that they provide a long-lasting immune response. mRNA vaccines are not live virus vaccines and do not interfere with human DNA. For more information on mRNA vaccines, see WHO’s explainer on the different types of COVID-19 vaccines.
Safety of COVID-19 vaccines for different groups
COVID-19 vaccines have been tested in large, randomized controlled trials that include people of a broad age range, all sexes, different ethnicities, and those with known medical conditions. The vaccines have shown a high level of efficacy across all populations. Vaccines have been found to be safe and effective in people with various underlying medical conditions that are associated with increased risk of severe disease. These include high blood pressure; diabetes; asthma; pulmonary, liver or kidney disease; and chronic infections that are stable and controlled.
Those who should consult with a doctor before vaccination include people with a compromised immune system, older people with severe frailty, people with a history of severe allergic reaction to vaccines, people living with HIV, and those who are pregnant or breastfeeding. For more information about vaccine safety for different groups, please see our Q&A on COVID-19 vaccine safety.
Pregnancy
You can get vaccinated whilst you are pregnant. 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. While there is less data available on vaccination of pregnant people, evidence on the safety of COVID-19 vaccines during pregnancy has been growing, and no safety concerns have been identified. Especially in countries with high transmission, or if you have an occupation where you are at more risk of being exposed to COVID-19, the benefits of getting the vaccine outweigh potential risks. There is no risk of getting COVID-19 from the vaccine. Talk to your healthcare provider to make an informed decision about vaccination.
Questions and Answers: COVID-19 vaccines and pregnancy
Breastfeeding
If you are breastfeeding, you should get vaccinated against COVID-19 as soon as it is your turn. 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 from the vaccine. In fact, the antibodies you get after vaccination may go through your breast milk and help to protect your baby.
Safety of COVID-19 vaccines for children
The Pfizer vaccine is safe for use in children aged 5 years and above. For children in this age group, WHO recommends a reduced dosage of 10 µg (0.2 ml). Both Pfizer and Moderna are safe for use in children aged 12 and above using a dose of 0.3 ml and 0.5 ml respectively. However, while the availability of COVID-19 vaccines is limited, WHO recommends that countries should vaccinate children only when high vaccine coverage with two doses has been achieved in higher priority-use groups, as identified in the WHO Prioritization Roadmap. However, children with existing health conditions should be prioritised for vaccination at the same time as other high risk groups.
Vaccine trials to determine whether other COVID-19 vaccines are safe for use in children are ongoing, and WHO recommendations will be updated when the evidence supports a change in the policy.
Practicing the protective behaviours is still the best way to keep everyone, including children, safe from COVID-19, whether or not you have been vaccinated. Keep a safe distance from others, avoid crowds, wear a well-fitting mask covering your mouth and nose, keep indoor spaces well ventilated, clean hands regularly and cover coughs and sneezes, as well as getting vaccinated as soon as it’s your turn.
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This page was updated on 21 January 2022 to reflect updates in the latest guidance relating to the vaccination of children.
