Booster vaccination: important questions and answers

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).

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.

A booster is a renewed vaccination against a pathogen. It is administered months after 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.

The Federal Vaccination Commission (EKIF) and the Federal Office of Public Health (FOPH) recommend that anyone aged 12 or over receive a booster vaccination with an mRNA vaccine if the initial immunisation was 4 months or more ago.

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.

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.

With regard to the virus variants to date, we now know that the mRNA vaccines provide very good protection against severe COVID-19 disease requiring hospitalisation. Depending on the age and variant, this protection afforded by the initial immunisation can diminish over time. For this reason, we recommend that everyone age 12 and over have a booster four months at the earliest after initial immunisation. This enhances and extends the vaccine protection. The booster vaccination gives you long-lasting protection against a severe case of COVID-19.

In the weeks following the initial immunisation, you are less likely to become infected with coronavirus than if you weren’t vaccinated. The risk of transmission to other people is also lower. This protection against infection, a mild case of the disease and transmission of the virus declines over time in everyone, and can be significantly reduced depending on the virus strain (e.g. with the Omicron variant).

The COVID-19 vaccines authorised in Switzerland were developed to work against the original virus (including the Alpha variant). It is clear that while the vaccines currently available provide less protection against the Omicron variant, the efficacy of the booster is good.

According to the latest data, in the first few weeks after full vaccination (initial immunisation) you’re well protected from infection, mild illness and severe illness requiring admission to hospital. Protection against infection and mild illnessdiminishes rapidly and substantially for everyone. Protection against severe illness likewise diminishes over time, but this happens less quickly, over several months, and the extent of the decline depends of the age of the vaccinated person.

With the booster you can increase your protection again. The risk of a severe case of COVID-19 requiring hospitalisation can be substantially reduced. In addition to this, after the booster you are also well protected again for several weeks against infection and mild cases of the disease. A booster is therefore urgently recommended from four months after initial immunisation.

So far it has not been possible to gauge how long the protection provided by the vaccines against severe illness requiring hospitalisation caused by Omicron lasts. After 3-4 months this efficacy is still very high. It is likely to last significantly longer than protection against infection with mild illness. 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.

Some vaccine manufacturers are already working on modified vaccines against new variants. However, 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?”

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.

Exceptions:

• People aged from 18 to 29 should preferably receive the Pfizer/BioNTech vaccine for their booster.
• The recommendation is for the Pfizer/BioNTech vaccine to be favoured for vaccinating those aged from 12 to 17.
• People who have been vaccinated with the Janssen viral vector vaccine are recommended to have their booster with an mRNA vaccine (Pfizer/BioNTech or Moderna), provided this is possible from a medical point of view.

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.

The recommendation is for the Pfizer/BioNTech vaccine to be favoured for vaccinating those aged from 12 to 17.

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

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 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.

If you have had a confirmed infection with coronavirus after 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 at the moment.

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

• In the event of infection within 4 months after initial immunisation, wait 4 months for your booster vaccination.
• In the event of an infection more than 4 months after initial immunisation, under the current recommendation the infection is deemed to be a booster. From a medical point of view, a booster is not required at the moment. Your immune protection was renewed by the infection.

On individual request, you can also receive a booster vaccination less than 4 months after infection, provided that the booster is administered from 4 months after the last dose of vaccine, if this is necessary, for example, for travel. However, there is no additional medical benefit.

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.

Cases of nettle rash have been reported after a booster vaccination, and a possible link is currently being investigated.

A second booster vaccination is neither authorised nor recommended in Switzerland at this time. At the moment it is unclear who will need further boosters with what vaccines in the future.

The efficacy of the mRNA vaccines is very good. The latest data show that very effective protection against a serious form of the disease requiring hospitalisation is afforded after initial immunisation and booster vaccination (i.e. usually after three vaccine doses).

According to our knowledge to date, a second booster vaccination does not provide any medical benefit for the currently circulating virus variants.

Since the Federal Office of Public Health (FOPH) and the Federal Commission for Vaccination (FCV) are constantly evaluating the latest data, any changes to the vaccination recommendations can be implemented without delay.

No, you should not wait. This is because it is not yet clear when adapted vaccines will be available or how they will be used. A booster with the current mRNA vaccines greatly enhances the protection against severe forms of the disease caused by Omicron.

The booster vaccination is recommended for anyone aged 16 years and older from 4 months after initial immunisation.

You are less well protected after one dose of the viral vector vaccine than after initial immunisation with an mRNA vaccine. For better protection, we recommend that between 28 days to 4 months after vaccination with the viral vector vaccine, you supplement the initial immunisation with a dose of an mRNA vaccine from Moderna or Pfizer/BioNTech.

To renew and extend the protection provided by the vaccine, we recommend a booster for anyone aged 18 years and older after initial immunisation with the viral vector vaccine. The booster increases and extends protection against falling ill with coronavirus.

We recommend a booster vaccination preferably with an mRNA vaccine (Pfizer/BioNTech or Moderna) from 4 months after full vaccination (initial immunisation), provided this is possible from a medical point of view.

Are you unable to be vaccinated with an mRNA vaccine for medical reasons? Or do you not want to be vaccinated with an mRNA vaccine? Then we recommend you have a booster with the Janssen viral vector vaccine from 2 months after initial immunisation.