Vaccines and immunization: Global vaccine safety

27 November 2019 | Q&A

Vaccination is a simple and effective way to protect people of all ages against harmful diseases before they come into contact with them. Vaccination is also safe. Side effects from a vaccine are usually minor and temporary, such as a sore arm or mild fever.

Any licensed vaccine is rigorously tested across multiple phases of trials before it is approved for use, and regularly reassessed once introduced. Scientists also constantly monitor information from several sources for any sign a vaccine may cause health risks, and if there is a concern, they take the appropriate investigative and corrective actions. These vaccine safety monitoring processes ensure that potential risks related to vaccination are kept to the minimum possible level. WHO works to make sure that vaccine safety systems exist everywhere so that anyone who receives a vaccine can have their concerns considered and investigated if needed.

To produce protection against a disease, vaccines activate biological reactions in the body. Those reactions vary depending on the type of vaccine and its mode of administration.

In addition to developing its protective effect, vaccine reactions may include soreness or a mild fever that resolves in a few days. Severe reactions occur very rarely (less than one in 100 000 doses of vaccines administered) and these generally occur in people with pre-existing diseases. If this risk factor is known beforehand, it is possible to prevent any potential reaction.

Proper vaccine storage, handling and administration is also important to ensure that vaccination is safe and effective. This is why WHO recommends that all health care personnel who administer vaccines receive comprehensive training before administering vaccines and are aware of their role in relation to monitoring for rare reactions.

Some side effects are so rare they can’t be detected even after studying the effects of a vaccine on tens of thousands of people. For that reason, the safety of vaccines continues to be monitored even after they are in routine use. Any reports of possible side effects made by parents and health providers are carefully reviewed and may signal the need for further investigation.

In addition, large populations of people who receive vaccines are often studied to identify any possible links between vaccination and rare or serious health conditions.

If a problem is suspected, a thorough investigation will take place by health authorities and medical experts. Investigations usually involve more tests of vaccine quality, manufacturing processes, and studies of vaccinated and unvaccinated people who have and have not had reactions.

It is important to respect parents and acknowledge their need for accurate information to guide the health decisions they make for their children. Babies and children need to get their vaccinations on time, so they get the best possible protection. It is important that health providers invite parents to share their questions and concerns during vaccination consultations and assure them that vaccines are the safest way to protect their children from infectious diseases.

Parents can be informed that all vaccines go through lengthy and rigorous testing processes and must pass through many clinical trials before they are approved for use.


The safety of vaccines is closely monitored by WHO, national regulatory agencies and vaccine manufacturers during the vaccine development phase and after vaccines have been registered and are utilized on a large scale.  Possible risks related to vaccines are carefully studied with the help of independent scientists.  A vaccine is registered in countries only if it does provide conclusive protection, if it is manufactured according to the highest standards, and if the risks related to its utilization are very low compared to the benefits.  

In addition, WHO provides public information about the known risks of vaccines and how to minimize those risks.  This information is updated as new data or new issues emerge or when improvements are made that can reduce those risks.  For WHO-recommended vaccines, see information sheets.

The Global Advisory Committee on Vaccine Safety (GACVS) is the independent expert group that has advised WHO for the past 20 years.  It meets twice annually and can be consulted any time a new concern is identified by WHO.  GACVS monitors the safety profile of all vaccines recommended by WHO.  Its recommendations are publicly available on its web site.

GACVS also publishes warnings every time a particular risk is identified or, importantly, when false rumours can affect the use of a safe vaccine. False rumours or wrong perceptions can endanger the population by depriving it of the protection vaccines provide.

GACVS is the driving force behind Vaccine Safety Net – a platform run by WHO assembling trusted web sites from all parts of the world providing reliable information about vaccines.  Those sites can be recognized because they display a WHO-protected visual identity.  As of 19 September 2019, there are 75 sites from 34 countries participating in this network, offering vaccine safety information in 24 languages.

The Blueprint 2.0 will be designed for all countries rather than concentrating on low- and middle-income countries.  It will focus on strengthening the capacities of national regulatory authorities, so the quality and safety of vaccines can be assured locally and closer to patients.  It will also foster the coordination of efforts between immunization programmes, regulatory agencies and their partners and highlight the responsibility of vaccine manufacturers in monitoring vaccine safety.  Coordination will include new mechanisms to ensure that vaccine safety strategies are fully operational and work effectively.  Finally, the strategy will highlight the role of communication and reliable information to dispel false allegations and wrong perceptions to sensitize people on vaccines’ tremendous benefits for individual and public health. 


The mechanisms to implement the strategy are already in place.  More funding will be mobilised to ensure success.

Basically, the new strategy is implemented through the Global Vaccine Safety Initiative (GVSI), a broad network of vaccine safety stakeholders who work jointly to improve vaccine safety in countries and globally.  The network develops new tools and methods, provides training, conducts studies related to current issues in vaccine safety, and promotes trusted communication based on science and objectivity.  The GVSI has demonstrated its value with the first Blueprint and is well equipped to address the challenges of the next decade.  In addition to implementing the strategy, progress will be monitored continuously.  The idea is that an independent group, convened by the GVSI Observatory, will do the monitoring.  That way, WHO and partners will receive regular information and advice from respected scientists, not directly responsible for Blueprint implementation, on how to better prioritize their efforts.    


Besides products with fewer untoward reactions, novel ways of administering vaccines are also under development.  These include pre-filled syringes that avoid any risk related to the transfer from a vial to a syringe.  Vaccine administration at the surface of the skin with patches is also at advanced stages of development.  The use of nucleic acid that can teach the body to produce self-protection against a disease is another avenue.

There will also be improvements in the way safety is monitored.  Larger and faster international information systems will take advantage of new information technology.  Agile reporting systems will increase the way vaccine safety concerns are notified.  International networks will be able to rapidly join forces and test, through computer-based records, if a possible reaction to a vaccine is found in all places that use the same product.

Finally, information about vaccines and vaccine safety will be increasingly accessible and verified.  People will benefit from trusted sources that use rigorous science to explain what is known about vaccine risks and how to minimize them.

The Summit has two main aims:

  • First, to enhance WHO’s work on vaccine safety.  WHO’s current vaccine safety strategy – called the Global Vaccine Safety Blueprint – was published in 2012.  The Blueprint has made enormous progress improving vaccine safety in low- and middle-income countries in the last eight years.  WHO now wants to look to the future and enhance its work to meet the challenges of the new decade and the sustainable development agenda.  These include the emergence of many new vaccines, a more interconnected world and the explosion of global communication.
  • Second, it will feature the most recent from state-of-the-art vaccine safety science as we transition to the next decade.  We have learned a lot in recent years and scientifically resolved many vaccine safety issues from the 20th and early 21st centuries.  New issues, primarily related to novel vaccines, have also appeared and require continuing research.  Today we have new tools and methods to resolve those questions quicker, more thoroughly and through broader partnerships.  A publication will be produced to inform the global health community about the current situation.