Effectiveness of spring 2024 (XBB.1.5) and autumn 2024 (JN.1) COVID-19 vaccination against hospitalisation in England.

BACKGROUND

In England, Omicron XBB.1.5 vaccines were offered through the spring 2024 COVID-19 vaccination campaign, targeting adults aged 75 and over and immunosuppressed individuals. The autumn 2024 campaign included adults 65 and over and clinical risk groups, offering Omicron JN.1 vaccines. This study evaluates vaccine effectiveness (VE) and waning protection of vaccines offered in the 2024 campaigns against COVID-19 hospitalisation.

METHODS

A test-negative case-control study design was used to estimate effectiveness of XBB.1.5 and JN.1 vaccines provided in the spring and autumn 2024 COVID-19 vaccine programmes respectively against COVID-19 hospitalisation. Logistic regression was used to calculate VE among eligible individuals hospitalised with COVID-19, where the exposure variable was vaccination status in the respective campaign and the outcome variable was SARS-CoV-2 test result, with adjustment for covariates. Separate analyses were conducted by manufacturer.

RESULTS

XBB.1.5 vaccines administered in spring 2024 conferred moderate protection, peaking at 45 % (95 % CI: 37-52 %) within 2-4 weeks, declining to 6 % (95 % CI: -11-21 %) by weeks 25-29. VE of Autumn 2024 JN.1 vaccines peaked at 43 % (95 % CI: 34-51 %) effectiveness at 10-14 weeks, falling to 34 % (95 % CI: 22-44 %) by 20 weeks; further monitoring is needed to evaluate long-term protection of the JN.1 vaccine. No significant differences in effectiveness were found between manufacturers in the autumn campaign.

CONCLUSIONS

The XBB.1.5 and JN.1 vaccines distributed during the spring and autumn 2024 COVID-19 vaccine campaign in England provided moderate protection against hospitalisation with COVID-19 among older adults eligible for the vaccines for at least 20 weeks after vaccination. The lower VE compared to earlier campaigns may reflect greater population-level immunity and heterogeneous lineage circulation during this period.