The previous updates used the term ‘vaccine effectiveness’, but this term will now be discontinued, since it suggests that it only measures how effective COVID-19 vaccination is in preventing hospital admissions. Now that the coronavirus SARS-CoV-2 has been present in the Netherlands for more than two years, however, most people have had the virus at least once or twice. This applies to vaccinated and unvaccinated people. People also build up immunity to COVID-19 after infection. There have been more infections among unvaccinated people, relatively speaking, because the COVID-19 vaccinations do offer some protection against infection. This is evident from the results of the VASCO study, among others. For privacy reasons, data on infections cannot currently be linked to data on vaccinations and hospital admissions. As a result, the figures cannot be corrected to account for previous infection, so the protective effects of vaccination cannot be differentiated from the protective effects of previous infections.
Relative risk difference
From now on, the updates will focus on descriptive tables and graphs showing the number of admissions by age group and by vaccination status. The relative risk difference (RRD) is used to indicate the difference in the risk of hospital or ICU admissions between groups that have a different vaccination status, without making any claims about which percentage of that can be attributed to vaccination. The RRD reflects differences in the burden of disease between groups that have a different vaccination status, and is therefore still useful for monitoring the COVID-19 situation in the Netherlands.
Booster jab or repeat vaccination reduces risk of hospital admission
In the past 8 weeks, from 1 June to 26 July 2022, people aged 12 years and older who had the booster jab had a 51% lower risk of hospital admission than people who only received the basic series of COVID-19 vaccinations (RRD -51%). The risk of hospital admission for people aged 60 years and older who had the repeat vaccination against COVID-19 was 25% lower than for people who received the booster jab (RRD -25%). This means that the risk of hospital admission after a booster jab was about 2 times lower during this period than for people who only received the basic series of vaccinations. In addition, the risk was about 1.3 lower for people aged 60 and older who had a repeat vaccination than for people in the same age group who had a booster jab but not a repeat vaccination. The risk of ICU admission after a booster jab was about 3.8 times lower than for people who only received the basic series of vaccinations (RRD: -74%). For people who received a repeat vaccination, the RRD for ICU admission compared to people who had the booster but not the repeat vaccination is still very uncertain due to the low numbers.
Everyone who has been invited to get a COVID-19 vaccination in the basic series, as a booster jab or as a repeat vaccination, but has not yet done so, can still get the jab. You can make an appointment via www.planjeprik.nl.