Expectations towards safety of vaccines

Key point

Although vaccines used in national immunization programmes (NIPs) are considered safe and effective, vaccines are not risk-free and adverse eventsAdverse event (or adverse experience)Any untoward medical occurrence that may appear during treatment with a pharmaceutical product but which does not necessarily have a causal relationship with the treatment. will occasionally occur following vaccination. Public trust in vaccine safetyVaccine safetyThe process of ensuring and monitoring the safety of vaccines. is key to the success of immunisation programmes.

Vaccines used in NIPs are safe and effective. However, like other pharmaceutical products, vaccines are not completely risk-free and adverse events will occasionally result from vaccination. Although most adverse events are minor (e.g. redness at injection site, fever), more serious reactions (e.g. seizuresSeizureUncontrolled electrical activity in the brain, resulting in convulsion, physical signs, thought disturbances, or a combination of symptoms., anaphylaxisAnaphylaxisAn acute, multi-system, allergic reaction (IgE mediated) to a substance, such as vaccination, drugs, and food. Symptoms of anaphylaxis may include breathing difficulties, loss of consciousness, and a drop in blood pressure. This condition can be fatal and requires immediate medical attention.) can occur albeit at a very low frequency.

The general public has low tolerance to any adverse events following vaccination because vaccines are given to healthy persons to prevent disease. For this reason, a higher standard of safety is expected of immunizations compared with medications that are used to treat people who are sick (e.g. antibiotics, insulin). This lower tolerance for risks from vaccines translates into a greater need to detect and investigate any adverse event following immunization (AEFI) than is generally expected for other pharmaceutical products.

National regulatory authorities (NRAs)National regulatory authority (NRA)The regulatory body that approves procedures to ensure that medicines, including vaccines, are of adequate safety and potency. The vaccine manufacturer is responsible for demonstrating that the vaccine batch produced meets the requirements, based on the test specifications given by the NRA. The NRA is also responsible both for the official vaccine lot release process, based on the data and information provided by the manufacturer and, eventually, for confirmatory testing. are responsible to ensure the quality, safety, and effectivenessVaccine effectivenessThe probability that a vaccine, when used in the field under routine vaccination circumstances, confers immunity in a population. Expressed as a percent. of vaccines and other pharmaceutical products. Before their introduction into an immunization programme, vaccines undergo several steps of evaluation to assess their safety and efficacyClinical efficacyThe ability of a medical intervention (e.g., vaccine, drug, procedure) to produce the desired clinical effect (e.g., protection, cure, symptomatic relief). in clinical trialsClinical trialA systematic study of a medical intervention in human subjects (including patients and other volunteers) in order to discover or verify the effects of and/or identify any adverse reaction to the intervention. Clinical trials also study the absorption, distribution, metabolism, and excretion of the products with the objective of ascertaining their efficacy and safety. Clinical trials are generally classified into Phases I to IV. Phase IV trials are studies performed after the licensure and introduction of pharmaceutical products. They are carried out to expand the evidence base of the product characteristics for which the marketing authorization was granted.. Once introduced, vaccines undergo very thorough and continuous reviews of their manufacturing process and NRAs and national immunization programme continue to monitor their safety. Adverse events following immunization are carefully investigated, their cause determined, and feedback provided to ensure that they are safe for the entire population.

Low public tolerance requires safe vaccination