Adverse effects of vaccinations

All vaccines can have adverse effects. However, only a small share of vaccine recipients will experience these. 

The most common symptoms after vaccination include 

• transient local symptoms in the injected limb, such as heat, redness, swelling and pain
• mild general symptoms such as feeling unwell, irritability, fatigue
• fever. 

Serious adverse effects, such as a severe allergic reaction, are very rare. 

The majority of symptoms are mild and short-term

Vaccines have different adverse effects typical of each vaccine. 

It is important that vaccine recipients or their guardians are sufficiently aware of possible reactions to vaccination and their symptomatic treatment in advance. This ensures that adverse reactions do not come as a surprise, and people can prepare for them.

After the adverse effect, a decision is made on whether to continue with the vaccination in the future. The decision is based on personal discretion. When making a further decision on vaccination, the benefits and possible adverse effects of vaccination are considered. When making the decision, the severity of the adverse reaction and the risk of recurrence are also assessed in relation to the consequences of the person getting the disease that the vaccine prevents.

It is very rare for the symptoms occurring after vaccination preventing the administration of follow-up vaccinations. 
Adverse effects by symptoms

Further information on the adverse effects of vaccines can also be found on the pages on individual vaccines.
Vaccines A to Z

Not all events or symptoms occurring after vaccination are caused by the vaccination. Symptoms are often caused by some another factor.

Monitoring and evaluation of vaccine safety 

The monitoring of vaccine safety is strictly regulated. 

A vaccine will only be licensed for sale once its safety has been assessed by the drug regulatory authorities. Once a vaccine has been introduced, the authorities will monitor the safety of the vaccine and its possible adverse effects. 

National and international cooperation is carried out in the safety monitoring and assessment of adverse reactions. 

This cooperation involves

• the authorities
• vaccine marketing authorisation holders
• national and international specialist organisations.

Individuals involved in detecting and reporting the adverse effects also include 

• doctors
• vaccine providers
• pharmacy staff i.e. pharmacists and dispensing chemists
• vaccinated people.

Reporting the adverse effects of vaccination 

The most common adverse reactions are already identified in vaccine trials before a vaccine is licenced for sale. Safety monitoring is important, as the rarest adverse effects will only become apparent once the vaccine has been widely used.
Pharmaceutical safety and information (Fimea)

Monitoring the safety of vaccinations in Finland

Finnish Medicines Agency Fimea is Finland’s pharmacovigilance authority.

Fimea maintains a national register of adverse drug effects to which reports filed on adverse drug reactions are stored. The register also includes reports of suspected or observed adverse effects to vaccinations. 

Fimea sends information about all the adverse reaction reports it receives to the European Medicines Agency EMA. EMA reports the adverse effects to the vaccine marketing authorisation holder and the World Health Organisation (WHO). The databases are searched for signals of any previously undetected adverse reactions. 

Any potential observations usually processed at the EU level. The pharmacovigilance authorities also process the data of the adverse effect reports in their periodic safety reviews, which assess the benefit–risk balance of the medicinal product. 

The Finnish Institute for Health and Welfare and Fimea cooperate in monitoring the safety of vaccines. The Finnish Institute for Health and Welfare is responsible for monitoring both the effectiveness and safety of the national vaccination programme and vaccinations. Fimea provides the Finnish Institute for Health and Welfare with information on the notifications of adverse reactions to vaccines and vaccinations. (Communicable Diseases Act 1227/2016)

The Finnish Institute for Health and Welfare also investigates adverse reactions using epidemiological methods, including register studies.