Covid booster shot halves chance of Omicron infection: RIVM

Vaccinated people who got a booster shot halved their chance of being infected with the Omicron variant of the coronavirus, researchers from the National Institute for Public Health and the Environment (RIVM) concluded. For people who previously recovered from a coronavirus infection, the advantage of a booster is smaller: their chance of infection decreases by 38 percent.

The researchers analyzed the data of over half a million people who had themselves tested at the GGD. The outcome confirms the view that vaccines and previous coronavirus infections provide less protection against the Omicron variant than against the Delta variant. The study also shows that people who became infected after getting vaccinated and later received a booster shot are most protected against the virus. This group is 76 percent protected against infection. People who never had the virus, as far as is known, are 68 percent less likely to contract it after a booster shot.

Coronavirus vaccines become less effective over time. Those who have only had the basic vaccination, for example, two doses of the Pfizer/BioNTech vaccine, are only 33 percent protected against an Omicron infection, according to the study. For unvaccinated people who had the coronavirus before, the protection is 25 percent. The question is how long the protective effect of the boosters will last. 

Previous studies showed that booster shots significantly reduce the chance of hospitalization due to Covid-19. In this study, the RIVM only looked at infections.