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.
The World Health Organization (WHO) has prequalified an additional novel oral polio vaccine type 2 (nOPV2), further strengthening the global supply of a vaccine at the heart of efforts to stop poliovirus type 2 outbreaks more sustainably and accelerate progress towards polio eradication.
All the ingredients in a vaccine play an important role in ensuring a vaccine is safe and effective. These ingredients, as well as the vaccines themselves, have been thoroughly tested and are monitored to ensure they are safe.
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.
Live-attenuated vaccine A live-attenuated vaccine uses a living but weakened version of the virus or one that’s very similar. The measles, mumps and rubella (MMR) vaccine and the chickenpox and shingles vaccine are examples of this type of vaccine. This approach uses similar technology to the inactivated vaccine and can be manufactured at scale.
Vaccination is one of the most effective ways to prevent diseases. Over the past 50 years, essential vaccines against just 14 diseases have saved at least 154 million lives (1). During the same period, vaccination has contributed to 40% of the drop in infant deaths. Together with governments, vaccine manufacturers, scientists and medical experts, WHO's vaccine safety programme is constantly ...