Booster vaccination: How effective is a third vaccination?

For better protection: The third corona vaccination, also known as a booster vaccination, has been available in all federal states since the beginning of November and can usually be administered six months after the second vaccination. Why a booster vaccination is necessary and why a refresher for other vaccinations is already common practice.

In Israel, the booster vaccination already contained the spread of the fourth corona wave in the summer. But even in Germany, booster vaccinations are not a new phenomenon. Even before the corona pandemic, boosters were not uncommon.

Booster vaccination necessary for many vaccines

The third corona vaccination is currently on everyone’s lips. The fact that a vaccination has to be refreshed again is the case with many vaccines. The body often needs multiple shots to boost memory cell responses. The memory cells of the immune system are specialized lymphocytes, which trigger a fast and effective immune response when they come into contact with the pathogen and put the body’s own defense system on alert.

A third vaccination or booster depends on several factors:

• Pathogen:  The more infectious a pathogen, the higher the protective effect should be. In addition, the structures of the viruses can change, so the vaccines should be adapted.
• Vaccine:  Live vaccines can be more effective than inactivated vaccines, which should therefore be boosted more often.
• Immune system :  Immunocompromised and elderly people often only build up a low level of immune protection. It is also advisable to refresh the basic immunization for them.

While the  flu vaccination  should be renewed annually, it is also advisable to refresh other vaccinations such as  tetanus , hepatitis,  pneumococci  and meningococci regularly, depending on the type of vaccine. An overview of all recommended vaccinations and their boosters can be found on the website of the  Federal Ministry of Health .

Corona: The booster is that effective

Initial results with almost 34,000 fully vaccinated people in Israel show that the effectiveness of the BioNTech/Pfizer vaccine can decrease: The probability of a breakthrough infection increases significantly after around four to five months:

• Age group over 60 years: The risk of a breakthrough infection is approximately 2.76 times higher in this age group than in people in the first few months after primary immunization.
• In the 40- to 59-year-old age group, the risk of infection increases by around 2.22 four to five months after the second vaccination.
• For the 18-39 year old age group, the risk of infection four to five months after full immunization is 1.67 times higher than before.

An increased infection rate of people who were vaccinated at the beginning of the vaccination campaign also indicates reduced vaccination protection in Israel.

After the detailed and successful results in Israel, Germany is also in favor of the third vaccination. The Standing Vaccination Commission (STIKO) recommends the booster vaccination, especially for older people and people with immunodeficiency, in order to minimize the risk of severe COVID-19 disease. Although there is still no final recommendation from the STIKO, the federal and state governments are already making it possible for anyone interested to have a booster vaccination six months after the basic immunization – the vaccine from BioNTech/Pfizer is recommended for people under 30 years of age.

The following graphic shows the vaccines approved in Germany and the factor by which the antibody response can be improved with a booster.

All  of the booster combinations described are sufficient and very effective.  There is currently insufficient data on people who received the  AstraZeneca vaccine. After the heterologous vaccination scheme and a booster with an  mRNA vaccine  at  Johnson  & Johnson shows a high level of effectiveness, this could also be the case with a booster on the AstraZeneca vaccine.

The booster vaccination is generally well tolerated – the most common  vaccination reactions  can be found here.