Vaccine effectiveness against COVID-19-related hospital admissions and deaths in the immunocompromised population: A retrospective, population-based cohort study in England

Problem

Individuals who are immunocompromised represent a vulnerable population at risk for severe COVID-19 outcomes. However, little research has been done on COVID-19 vaccine uptake and effectiveness of in people with conditions of immunocompromise. We aimed to describe COVID-19 vaccine uptake in the population and determine vaccine effectiveness in preventing severe COVID-19 outcomes in immunocompromised population using a nationally representative, population-based cohort in England.

Approach

We used the QResearch primary care database using records from people aged 12 or older during the study period (December 1, 2020, to April 11, 2022). Vaccine uptake was the proportion of the immunocompromised population (people taking immune-modifying drugs or chemotherapy treatments, organ transplantation or dialysis) that received one or more COVID-19 vaccinations. A matched case-control design was used to estimate odds ratios (OR) for the calculation of vaccine effectiveness (100%*[1-OR]) for severe COVID-19 outcomes (COVID-19-related hospitalisation and death) in people who had been vaccinated versus those who had not, accounting for vaccine doses and time periods since vaccination.

Findings

The analysis included 583,541 people with conditions of immunocompromise. Among this population, 546,885 (93.7%) were vaccinated, and 36,656 (6.3%) were unvaccinated. During the follow-up period, 17,886 immunocompromised patients were hospitalised and 5,478 died due to COVID-19. In this population, vaccine effectiveness against COVID-19 hospitalisation was 62% (95% CI 52–70; compared to the unvaccinated) after 6 to 14 weeks of the first vaccination; 77% (72–81) after 6 to 14 weeks of the second dose; and 78% (73–82) after 6 to 14 weeks of receiving the third dose, before waning to 59% (43-71) after the 14th week. Across all doses, vaccine effectiveness against COVID-19-related death in the immunocompromised population was highest 2 to 6 weeks after vaccinations: 76% (70-81) after the first dose; 90% (85-93) after the second dose; and 91% (89-94) after the third dose compared to those unvaccinated. Protection against COVID-19-related death continued to remain high after receiving the third dose (85% [79-89] after 18 weeks of vaccination).

Consequences

Our findings suggest that COVID-19 vaccines are highly effective at preventing COVID-19 hospitalisation and death in immunocompromised people, who should be encouraged to take up COVID-19 vaccinations to reduce their risk of severe COVID-19-related outcomes. This study is, to our knowledge, the largest study assessing COVID-19 vaccine effectiveness in an immunocompromised population. Stratified analyses of vaccine effectiveness in different subgroups of immunocompromised conditions and by time periods of different dominant COVID-19 variants are ongoing.