Vaccine effectiveness in preventing hospital admission has been slightly lower in the last 8 weeks compared to the entire period from 11 July to 21 December 2021. One factor that may play a role is that the date on which people completed their basic vaccination series is longer ago. Another possible factor is the higher virus circulation in recent weeks. Vaccine effectiveness in preventing ICU admissions remains high for all age groups.
Vaccine effectiveness in preventing hospital admissions is lower among people aged 70 years and older than among people under 70. In the past eight weeks, it was 81% against hospital admission, compared to 84% between 11 July and 21 December. Possible effects of a booster vaccination have not yet been included in this update.
In the hospital admissions up to 21 December, it is unlikely that the Omicron variant played a significant role.
The analysis is based on NICE data on hospital admissions of patients with COVID-19 admitted until 21 December 2021. The data was enriched on 22 December 2021 with vaccination data from the COVID-19 Information and Monitoring System (CIMS). The method used to calculate vaccine effectiveness is explained in the report: Study: Effectiveness of COVID-19 vaccination against hospital and ICU admission in the Netherlands
More information is available in previous updates on effectiveness of COVID-19 vaccines.
* These probabilities can be derived directly from vaccine effectiveness: reduced probability=100/(100-vaccine effectiveness).