How the vaccine works
The Comirnaty vaccine works by strengthening the body’s ability to defend itself against infection with coronavirus (COVID-19).
Prior to its authorisation, Comirnaty was tested in major clinical trials with more than 36,000 voluntary trial subjects, and the vaccine demonstrated 95% efficacy against coronavirus after the second vaccine dose. In other words, there were 95% fewer cases of COVID-19 among the trial subjects given the real vaccine than among those given a placebo.
If you have been vaccinated, you can still get ill if you are exposed to virus, but you will typically have milder symptoms than if you had not been vaccinated.
The benefits that the vaccines bring to the entire population are fewer hospital admissions, fewer severe disease cases and fewer deaths. The higher the infection rate, the greater the impact of vaccinating people, in overall terms.
The vaccine has so far proved to be resistant to the various virus variants and mutations that have emerged in Denmark. However, its efficacy against infection from new variants is lower than its efficacy against the original variant.
The variant-updated covid-19 vaccine from Pfizer/BioNTech targets the corona variant Omikron XBB.1.5, but also protects against other known corona variants that are currently in circulation. The vaccine is approved by the EU Commission. You will find the current status of all approved covid-19 vaccines – including the variant-adjusted ones – on the website of the European Medicines Agency EMA.
In the 2023/24 season, you get one dose, regardless of whether you have previously been vaccinated.
Common side effects to expect after vaccination
All vaccines can cause side effects; the Comirnaty vaccine is no exception.
It is expected that more than half of those vaccinated will get mild side effects lasting for a few days such as tenderness where the injection was given, tiredness and headache.
About one in ten can expect to develop a fever and swelling at the injection site after vaccination.
Mild and moderate side effects, that pass within days, are common after vaccination and usually completely harmless. So, if you develop a mild fever or your muscles ache, this is a sign that your immune system is reacting. There is no need to contact your doctor about this. Further information about the mild and moderate side effects is provided in our information sheet and in the vaccine’s summary of product characteristics at www.ema.europa.eu.
If, on the other hand, you experience serious symptoms after vaccination, you should contact a doctor. Examples are allergic reactions like shortness of breath, swelling of the face or on the neck and rash.
Please read the product information for details on all the known side effects (see link at the top of the page).
Update of the covid-19 vaccine
Prior the 2023/24 winter season, a new update of the covid-19 vaccine from Pfizer/BionNTech has been approved.
It has been approved by the EU Commission on 1 September 2023: Adapted COVID-19 vaccine for autumn vaccination compaigns * (europa.eu) after it had been assessed and recommended by the EMA: Comirnaty: EMA recommends approval of adapted COVID-19 vaccine targeting Omicron XBB.1.5 | European Medicines Agency (europa.eu).