Impact of COVID-19 vaccination on COVID-19 hospital admissions in England during 2021: an observational study

Abstract

Objectives: To examine the impact of COVID-19 vaccination on hospital admissions in England in 2021.

Design: Observational study of emergency admissions for COVID-19 by vaccination status in people 16 years and over in England.

Setting: Hospitals in England.

Participants: A total of 48.1 million people registered with an English GP, aged ≥16 years with a recent NHS contact.

Main outcome measures: Emergency hospital admissions with a primary diagnosis of COVID-19 between 1 January and 31 December 2021. Monthly admission rates were directly standardised for age, sex, risk category and vaccination dose to estimate vaccine effectiveness (VE) over time, between vaccine doses, age groups and risk groups.

Results: A total of 192,047 hospital admissions were included. The unvaccinated admission rate was higher in December 2021 (6.1 admissions per 100,000 person-days; 95% CI: 5.9 to 6.3) than January 2021 (4.9; 95% CI: 4.9 to 5.0). Vaccinated admission rates were ≤1 per 100,000 from February to December. Doses 1 and 2 VE waned over time, particularly in older and clinically vulnerable groups (although this may reflect that they were vaccinated earlier). Dose 3 VE remained above 93%.

Conclusions: COVID-19 hospitalisations were consistently highest in the unvaccinated. Despite high case rates at the end of 2021, overall admission rates remained stable, driven by low admission rates among vaccinated people. There is population-level waning in VE, recovering after subsequent doses, potentially more marked in older and at-risk groups. The findings support JCVI (Joint Committee on Vaccination and Immunisation) guidance for an ongoing booster programme, especially in older people and higher clinical risk groups.

Keywords: Infectious diseases; public health; vaccination programmes.

Figure 1.

Coverage of COVID-19 vaccination doses over time in the English population aged 16 years and over. Dose 1+ equals total number of first doses administered, Dose 2+ equals total number of second doses administered, Dose 3+ equals total number of third doses administered.

Figure 2. Directly standardised admission rates per 100,000 person-days by COVID-19 vaccine status. Rates were standardised for month, vaccination status, age, sex and risk group. The COVID-19 case rate is shown as a dashed line. Bars are shown with 95% confidence intervals. Dose 1 equals those who received only one dose, Dose 2 equals those who received only two doses, Dose 3 equals those who received three or more doses.

Figure 3.

Vaccine effectiveness by vaccination dose and month, January 2021 to December 2021. Shaded regions indicated 95% confidence intervals. Dose 1 equals those who received only one dose, Dose 2 equals those who received only two doses, Dose 3 equals those who received three or more doses.

Figure 4.

Vaccine effectiveness (VE) per age group and vaccination dose from 1 to 31 December 2021. Bars are shown with 95% confidence intervals. (Note: For the 16–17-year-old group, only 10.6% had two doses and 0.4% had 3+ doses, with <10 admissions so VE was not calculated). Dose 1 equals those who received only one dose, Dose 2 equals those who received only two doses, Dose 3 equals those who received three or more doses.

Figure 5.

Vaccine effectiveness per risk group and vaccination dose for the period of 1 to 31 December 2021. Bars are shown with 95% confidence intervals. NB: ‘Lower Risk’ refers to individuals who are not in a high-risk group. Dose 1 equals those who received only one dose, Dose 2 equals those who received only two doses, Dose 3 equals those who received three or more doses.