In the period from 1 February 2022 to 5 April 2022, vaccine effectiveness of the basic series of COVID-19 vaccinations in preventing hospital admission was 35%. After the booster vaccination, that percentage was 81%. Vaccine effectiveness against ICU admission was 45% after the basic series, compared to 90% after booster vaccination. This means that the risk of hospital admission after a booster jab is more than 3 times lower than for people who have only received the basic series of vaccinations. This means that the COVID-19 booster vaccination still helps to prevent hospital and ICU admission due to COVID-19, and continues to be effective after three months. However, protection is somewhat lower in all age groups 10 to 14 weeks after the booster vaccination. 

The decrease in vaccine effectiveness in preventing hospital and ICU admission can probably be attributed to waning effectiveness over time. Another partial explanation could be that many people who were not vaccinated against COVID-19 recently had a SARS-CoV-2 infection and built up immunity as a result. 

Very few people aged 60 and over who received a repeat vaccination against COVID-19 have been admitted to hospital. In people aged 70 years and older, the repeat vaccination seems to restore vaccine effectiveness against hospital admission to the level just after the booster vaccination. Due to the small numbers involved, exact figures on vaccine effectiveness of the repeat vaccination against COVID-19 have not yet been established.