How the vaccine works
The COVID-19 vaccine from Moderna works by strengthening the body’s ability to defend itself against infection with coronavirus (COVID-19).
Prior to its authorisation, the Moderna vaccine was tested in major clinical trials with more than 28,000 voluntary trial subjects over the age of 18, and the vaccine demonstrated 94% efficacy against coronavirus two weeks after the second vaccine dose. In other words, there were 94% 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, including the Omicron variant. However, its efficacy against infection from new variants is lower than its efficacy against the original variant.
That’s why Moderna, the company behind the vaccine, is currently updating the vaccine to make it protect just as well or better as the original vaccine. These new variant-updated vaccines must meet the same high quality requirements as those for the original vaccine.
Common side effects to expect after vaccination
All vaccines can cause side effects; the Moderna 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.
Between one and two in ten individuals are likely to develop a fever.
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 our information sheet or the product information for details on all the known side effects (see links below).