Amsterdam UMC, together with three other academic centres, is investigating in the SWITCH study whether a second corona vaccination after a first Janssen vaccination is useful. Employees of the umbrella centres who have already received their first shot of Janssen will receive a second vaccination with Janssen, Pfizer or Moderna.

With three of the four Covid-19 vaccines registered in the Netherlands, it is necessary to administer two vaccinations for a good immune response against SARS-CoV-2. Janssen's vaccine is the only vaccine that provides sufficient protection against Covid-19 with only one administration. Due to the increasing circulation of certain variants of the coronavirus, additional vaccination may be necessary after one shot of Janssen. A collaboration consisting of four academic centres in the Netherlands (Erasmus MC, UMC Groningen, LUMC and Amsterdam UMC) investigates this in the SWITCH study.


Normally someone gets the same Covid-19 vaccine twice, but there are several reasons why combining different vaccines can be useful. Bram Goorhuis, internist-infectiologist at Amsterdam UMC: ''Mixing vaccines makes vaccination campaigns more flexible, speeds up the vaccination process and reduces the impact of delivery problems."

Due to the rare side effects after vaccination with AstraZeneca, a number of countries have already investigated whether an mRNA vaccine such as Pfizer or Moderna can follow an initial vaccination with AstraZeneca. The first studies show that this proved to be a good and safe approach to elicit a strong immune response without serious side effects. Because a large group of people in the Netherlands are vaccinated with the Janssen vaccine, the researchers here will study whether various other vaccines (Janssen, Pfizer or Moderna) can be used after the Janssen vaccine.

Improved immune response

The SWITCH study has been set up in consultation with the international studies that are running on combining different vaccines. Thanks to financial support from ZonMw, the researchers will carry out this study among hospital staff from the four different academic centres. The researchers will mainly study whether the combinations are safe and whether this elicits a good immune response. They will also study the immune response against the different coronavirus variants, because combining vaccines could lead to a broader immune response. The first results of this study are expected at the end of October.