RIVM monitors how effective COVID-19 vaccines are in protecting against COVID-19. Effectiveness is monitored by analysing data from different registries and by conducting specific research. The results are used to formulate policy on COVID-19 vaccination. RIVM  is also conducting research in various ways to monitor the spread of the coronavirus SARS-CoV-2. See Research on COVID-19

In autumn 2021, most people in the Netherlands have had the opportunity to be vaccinated against COVID-19. It is important to monitor the effect of the vaccination(s). This is because vaccinations may become less effective over time. Or new variants of the virus could emerge, reducing the protection offered by vaccination.

Updates of these research results are published regularly on this website.

How is RIVM researching protection by COVID-19 vaccinations?

RIVM compares the risk of infection with the coronavirus SARS-CoV-2 in people who are vaccinated and people who are not vaccinated. Researchers look at the probability of various outcomes, such as illness, hospital admission, and transmission of the virus.

Various sources are used, including data from the Municipal Public Health Services (GGDs) about testing and vaccinations, and data about hospital admissions.

Additional information is also collected by means of surveys and blood tests, through the Vaccination Study on the Coronavirus (VASCO) and through research on risk factors for COVID-19 (the CONTEST study).

In the VECTOR study, RIVM is also collecting additional data from people admitted to hospital to investigate the effectiveness of COVID-19 vaccination in protecting people in high-risk groups against hospital admission.

Researchers are investigating COVID-19 protection in different groups of people. This includes the type of vaccine and how long ago vaccination took place.

Overview of studies and research results

Vaccination-induced protection against infection

Boosters improve diminished protection against Omicron infection after basic COVID-19 vaccination or previous infection.
Vaccination or previous infection with the coronavirus SARS-CoV-2 provide less effective protection against the Omicron variant compared to the Delta variant. A COVID-19 booster vaccination ensures renewed protection against Omicron. 

In December 2021, results were reported on protection by COVID-19 vaccinations from 4 July 2021 to 2 December 2021. The Delta variant of the coronavirus SARS-CoV-2 was the dominant strain in the Netherlands during that period. Vaccination offers more than 80% protection against an infection with the virus among people under 70 years old who are tested due to symptoms. Among people over 70, vaccination offers 73% protection.

Vaccine-induced protection against an infection with the Delta variant of the coronavirus

In June 2021, results were reported on the Pfizer/BioNTech vaccine (Comirnaty®) and protection against COVID-19 among older people living at home. People over 75 years old living at home were 82% protected against a coronavirus infection from three weeks after the second vaccination. 

Effectiveness and impact of COVID-19 vaccination among older people in the Netherlands (January-May 2021)

Vaccine-induced protection against hospital admission

Vaccine effectiveness in preventing hospital admissions (July-October 2021)

Vaccine-induced protection against transmission of the coronavirus SARS-CoV-2

In August 2021, RIVM reported on protection by COVID-19 vaccines against coronavirus transmission from February to May 2021. During that period, the Alpha variant was the dominant strain circulating in the Netherlands. Data from source and contact tracing by the Municipal Public Health Services (GGDs) was used for this study. People living in the same household as people who were fully vaccinated were 71% less likely to be infected than household members of unvaccinated people.

A follow-up study in August and September 2021 showed that vaccination also significantly reduced transmission of the Delta variant. This study showed that fully vaccinated people who tested positive for the coronavirus SARS-CoV-2, despite vaccination, were 63% less likely to transmit the virus to unvaccinated household members than people who also tested positive, but were not vaccinated.

COVID-19 vaccination reduces transmission

Vaccination reduces transmission to unvaccinated household members by 63% for Delta variant


VASCO, the Vaccination Study on the Coronavirus, is researching the long-term effectiveness of COVID-19 vaccines in the population of the Netherlands.

Read more about Vaccination Study on the Coronavirus (VASCO)


The CONTEST study is investigating which risk factors are important for contracting COVID-19. In this study, researchers are also calculating COVID-19 vaccine effectiveness in preventing infection.

Read more about the 


The VECTOR study investigates vaccine effectiveness against COVID-19 related hospital admissions in risk groups.

The VECTOR study investigated protection against hospital admission based on data from six hospitals from 1 March to 5 July 2021. During this period, the Alpha variant was the dominant strain in the Netherlands. The study showed that vaccine effectiveness against COVID-19 related hospital admissions was 93% for full vaccination and 70% for partial vaccination. Of the 379 COVID-19 patients, 334 were not vaccinated, 40 were partially vaccinated and 5 were fully vaccinated. All fully vaccinated patients and 39 out of 40 partly vaccinated patients had an underlying health condition. Many of the unvaccinated patients also had underlying health conditions. This was not the case for 14% of the unvaccinated patients. There were no ICU admissions among fully vaccinated COVID-19 patients. 19% of the unvaccinated patients ended up in the ICU. 

Read more about the VECTOR Study