Vaccine effectiveness against hospital admission remains high

Vaccination offers effective protection against illness caused by SARS-CoV-2 infection, and is very effective in preventing severe COVID-19. 84% of all people in the Netherlands aged 18 years and older are now vaccinated. This percentage is still rising slowly.

New analyses of hospital and ICU admissions up to and including 31 October 2021 show that COVID-19 vaccination continues to be very effective in preventing hospital admission (94%) and ICU admission (97%), with effectiveness remaining nearly unchanged in July through October. This means that the risk of hospital admission with COVID-19 is 17 times lower for fully vaccinated people than for non-vaccinated people. The risk of ICU admission is 33 times lower.

Vaccine effectiveness against hospital admission in the age group of 70 years and older is 89%. This percentage is less high than vaccine effectiveness in younger age groups. The risk of hospital admission was more than 9 times higher among unvaccinated people aged 70 years and older than among vaccinated people in the same age groups. Out of every 100,000 people aged 70 and older who are not vaccinated, or are not fully vaccinated, an average of 5.1 people per day were admitted to hospital with COVID-19 in October (Figure 1). This number was 6.0 for unvaccinated people and 0.89 for partly vaccinated people. Out of every 100,000 vaccinated people aged 70 and older, an average of 0.82 people per day were admitted to hospital with COVID-19 in October.

Figure 1. Average number of people per day admitted to hospital with COVID-19 in October 2021, per 100,000 people with the same vaccination status in the population, divided by age category.

Despite full vaccination, people may still get a SARS-CoV-2 infection, and may sometimes be admitted to hospital. Because more and more people are vaccinated, the percentage of vaccinated people who are admitted to hospital is increasing. Since the beginning of the epidemic, older people (and vulnerable people) have been more likely to be hospitalised with COVID-19. Even after vaccination, this pattern remains visible. Older patients now comprise a higher percentage of all patients admitted to hospital.

Age and vaccination status of patients admitted to hospital

The unvaccinated COVID-19 patients (median age 59 years in October) are significantly younger than fully vaccinated COVID-19 patients admitted to hospital (median age 77 years in October).

With the rising number of SARS-CoV-2 infections, there has been a relatively sharp increase in the number of people admitted to hospital in the age group of 70 and older (Figure 2). More than 90% of everyone aged 70 years and older has been fully vaccinated, but vaccines offer slightly less effective protection in older people (vaccine effectiveness is 89% among over-70s) than in people aged 50-69 (96%) and people aged 12-49 (97%). As the number of older patients in hospital increases, the percentage of fully vaccinated patients is also increasing.

 

Figure 2. Daily number of COVID-19 hospital admissions among people who are fully vaccinated and people who are not fully vaccinated, by age group, 1 September to 31 October 2021. Not all hospital admissions at the end of October have been reported by the hospitals yet. 

In October 2021, 16% of the Dutch population aged 18 years and over was not vaccinated against COVID-19, or had not yet been fully vaccinated. Over half (56%) of COVID-19 patients in hospital that month had not been vaccinated or had not been fully vaccinated (Figure 3). In September, that percentage was 73%.

70% of COVID-19 patients in ICU were not vaccinated (or not fully vaccinated) in October (Figure 4), compared to 83% in September.

The percentage of fully vaccinated patients admitted to hospital with COVID-19 is not an indication of the extent to which vaccination protects against hospital admission. The only measure that can be used for this is vaccine effectiveness, which is still high. The latest analyses show that vaccine effectiveness recently dropped very slightly (93% for hospital admission and 96% for ICU admission in the last 8 weeks, which is 1 percentage point lower than for the whole period from July-October), and that vaccine effectiveness decreases slightly over time, based on how long it has been since vaccination. This may also be a consequence of the high infection rate at this time.

Figures 3 and 4. Distribution of vaccination status for COVID-19 patients admitted to hospital (Figure 3) and ICU (Figure 4) in October 2021. In total, 1.952 COVID-19 patients were admitted to hospital in October 2021, and the vaccination status of 1.926 of those patients (99%) was known. In the same period, 353 COVID-19 patients were admitted to ICU, and the vaccination status of 346 (98%) was known. During this period, 21 COVID-19 patients admitted to hospital were partially vaccinated, including 2 in the ICU.

Data used for this page comes from NICE data on hospital admissions of patients with COVID-19 admitted until 31 October 2021, as available on 1 November 2021, enriched with vaccination data from the central COVID-19 vaccination register (CIMS). More information on how the data is generated can be found in this report on vaccine effectiveness.

Would you like to know more? Watch the video: Percentage of vaccinated people in hospital