Last updated on 20.01.2022

Booster vaccination: important questions and answers

For the best possible protection, especially against severe COVID-19 disease involving hospitalisation, a booster vaccination with an mRNA vaccine from Moderna or Pfizer/BioNTech is recommended from 4 months after full vaccination (initial immunisation).

Responsibility for administering the booster lies with the cantons. Find out from your canton’s website or infoline where you can register and get vaccinated. Or ask your doctor or pharmacist.

Do you still have questions related to the booster vaccination? Below are most important questions and answers with straightforward explanations.

What is a booster vaccination and what is its purpose?


A booster vaccination is an extra dose of a vaccine. If possible it should be administered before the protection provided by initial immunisation diminishes. Its purpose is to maintain or restore, and prolong, the protection provided by the vaccine. Other vaccinations besides the one for COVID-19 also lose their effect over time and should be renewed. For example, the FOPH recommends getting regular boosters for the vaccination against diphtheria and tetanus (lockjaw).

What’s the difference between initial immunisation and the booster?


Initial immunisation involves one or more vaccinations that result in the establishment of optimum immune protection against a specific pathogen and its consequences. It triggers an immune response that confers both rapid protection and an immune memory. The immune protection achieved can last for a varying length of time depending on the vaccine and the pathogen. It can be maintained or increased again with a booster vaccination.

booster is a renewed vaccination against a pathogen. It is administered months after full initial immunisation to refresh the immune protection. The booster vaccination reactivates the immune memory created by initial immunisation, and this quickly restores and prolongs immune protection. Some vaccinations work a whole life long, while others have to be refreshed. A booster vaccination differs from initial immunisation in that it leads to sufficient immune protection again within a short period of time with the administration of a (possibly smaller) single dose of vaccine.

Who is recommended to have a booster vaccination against COVID-19?


The Federal Vaccination Commission (EKIF) and the Federal Office of Public Health (FOPH) recommend that anyone aged 16 or over receive a booster vaccination with an mRNA vaccine if the initial immunisation was 4 months or more ago.

Why should I have a booster vaccination? What are the benefits of a booster for me?


The booster vaccination reminds the immune system of the pathogen. This increases and prolongs your immune protection. The booster helps give you longer-term protection from a severe case of COVID-19. In the short term the booster can also increase your protection against infection and mild cases of the disease and the consequences, as well as temporarily reducing circulation of the virus.

Why should I get a booster vaccination if my certificate is still valid?


With the booster vaccination you can improve your individual protection against the coronavirus and – at least temporarily – also reduce transmission of the virus to other people.

The mRNA vaccines provide very good protection against severe COVD-19 disease requiring hospitalisation. In people aged 65 and over, however, it is emerging that this vaccine protection can diminish over time. So far it’s unclear whether the protection from severe cases of the disease also diminishes for people under 65 and new variants of the virus. However, protection from mild cases and transmission of the virus declines over time for everybody. Protection from the Omicron variant does not last as long as for previous variants. The booster can help increase protection against infection and mild disease and the consequences (e.g. long COVID, the long-term effects of COVID-19) and temporarily reduce circulation of the virus.

Does the booster also work against Omicron?


Current data on the protection the vaccines provide against infections with the Omicron variant show lower efficacy than against infections with the Delta variant. But according to current knowledge, you are well protected against infection with Omicron in the first few weeks after a booster vaccination. It is still not clear how long this protection lasts.

According to initial studies, protection from severe cases of the disease should remain largely intact. How good the protection against severe COVID-19 disease actually is remains to be seen in practice.

The long-term efficacy of the booster vaccination against Omicron is not yet known; some vaccine manufacturers are already working on adapted vaccines. It is still unclear whether their use will be necessary in the future.

For more information on protection against the Omicron variant, see the question “How well am I still protected if I haven’t had a booster?”

What vaccine should I have the booster with?


Basically the same vaccine should be used for a booster vaccination with an mRNA vaccine as for initial immunisation, i.e. the first vaccination(s). If the same vaccine is not available, however, the other mRNA vaccine can also be used. As for initial immunisation, the recommendation is for the Pfizer/BioNTech vaccine to be favoured for vaccinating those under 30.

I am under age 30. Can I still have a booster with Moderna or does it have to be Pfizer/BioNTech?


People under age 30 are recommended to favour a booster vaccination with the Pfizer/BioNTech vaccine, as is the case with initial immunisation. This is because in very rare cases, inflammation of the heart muscle or the pericardium has been observed in the 14 days after the vaccination. Most of these cases were mild and could be treated effectively. Among people under age 30 such inflammations were observed more frequently after vaccination with the Moderna vaccine. The recommendation that the Pfizer/BioNTech vaccine should be favoured for people under 30 may help reduce this very small risk even further.

What is most important at the moment, however, is that as many people as possible get a booster from 4 months after initial immunisation, regardless of which mRNA vaccine is used. People under 30 can also receive the Moderna vaccine if the Pfizer/BioNTech vaccine is not available at the vaccination centre. Inflammation of the heart muscle or pericardium occurs much more frequently after infection with the coronavirus than after vaccination.

Does the recommendation for the booster vaccination also apply to pregnant women?


The booster vaccination is also recommended for pregnant women from the second trimester and for women who are breastfeeding.

I have recovered from COVID and have had one dose of vaccine. Does a second vaccination now count as a booster?


A confirmed coronavirus infection and one dose of an mRNA vaccine at an interval of at least 4 weeks (regardless of the sequence) results in complete initial immunisation. In this case, a second vaccination corresponds to a booster for people who have recovered if it is administered from 4 months after full initial immunisation.

After full vaccination I got infected with the coronavirus. Should I have a booster, or does the new infection count as a booster?


If you have had a confirmed infection with coronavirus after full initial immunisation, the following applies:

  • If you got the infection within 4 months of initial immunisation, a booster vaccination is recommended 4 months after this infection.
  • If you got the infection more than 4 months after initial immunisation, generally no booster is necessary. However, in this case a booster vaccination certificate cannot be issued, as both the recovery certificate and the still valid vaccination certificate are sufficient for admission to 2G events. If the infection was less than 120 days ago (according to your recovery certificate) you are exempt from additional testing for 2G+ during this period, as are people who had their booster vaccination less than 120 days ago.

What side effects can be expected after the booster vaccination?


The same side effects can occur after the booster as after the vaccination(s) for initial immunisation. In most cases they are mild and last only a short time. These are normal signs that the body is building the desired protection against the coronavirus.

Will further boosters be necessary in the future?


At the moment it is unclear who will need further boosters with what vaccines in the future. There is still no data on the efficacy of three doses of vaccine over a longer period and against variants of the virus.

Should I wait with the booster vaccination until a new vaccine is available that has been adapted for new variants?


No, you should not wait. The booster vaccination is recommended for anyone aged 16 years and older from 4 months after initial immunisation. The booster vaccination increases protection against COVID-19. Initial data on the effectiveness of the booster vaccination also show a strong increase in protection against infection, at least temporarily, against the Omicron variant. While it has so far not been possible to assess the efficacy against severe disease involving hospitalisation, it is likely to be significantly higher than the efficacy against infection leading to a mild case of the disease. With earlier variants (e.g. Delta), the efficacy against severe disease involving hospitalisation was significantly higher and longer lasting than the efficacy against mild disease.

It is not yet clear when adapted vaccines will be available or how they will be used.

How well am I still protected if I haven’t had a booster?


Delta variant:
The risk of a severe case of the disease is significantly higher in older people whose initial immunisation dates back more than 6 months than in those who have had a booster vaccination. People who were vaccinated more than six months ago and who have not received a booster also have a higher risk of becoming infected with coronavirus and passing the virus on than those who have had a booster.

Omicron variant: 
There are constantly new findings on the Omicron variant. Initial studies suggest that in both people who have recovered and have not been vaccinated and those vaccinated twice, protection against Omicron is initially good, but then declines more rapidly and is eventually lower than against Delta. Anyone who four months after initial immunisation has had a booster or a coronavirus infection has better protection against infection with Omicron. However, it is lower than the protection against infection with earlier virus variants. According to current knowledge, you are well protected against infection with Omicron in the first few weeks after a booster vaccination.
There is not yet much data available on the protective effect of initial immunisation against severe infections with Omicron. Initial studies show that people with full initial immunisation continue to be very well protected against severe cases of Omicron infection, although protection is somewhat lower than against Delta.

You’ll find more information around the booster vaccination here: