- Andrew N
- Stowe J
- Kirsebom F
- et al.
In the week commencing January 3, 2022, an increase in sequenced cases of Omicron sublineage BA.2 was observed.
SARS-CoV-2 variants of concern and variants under investigation in England: Technical Briefing 35.
BA.2 has a growth advantage over BA.1
SARS-CoV-2 variants of concern and variants studied in England: technical briefing 36.
,
- Lyngse FP
- Kirkeby CT
- Denwood M
- et al.
and has become the dominant variety in the UK at the time of writing. Neutralization assays using monoclonal antibodies have suggested a small antigenic difference between BA.1 and BA.2, although sera from booster subjects similarly neutralize both variants.
SARS-CoV-2 variants of concern and variants studied in England: technical briefing 36.
The UK COVID-19 immunization program has been in place since 8 December 2020 with two dose primary series of either BNT162b2 (Comirnaty, Pfizer–BioNTech), ChAdOx1-S (Vaxzevria, Oxford/AstraZeneca) or mRNA-1273 (Spikevax, Moderna). The booster dose of either BNT162b2 or a half dose (50 μg) of mRNA-1273 was introduced on September 14, 2021 for adults over 50 and at risk groups and on November 29, 2021 for all adults.
- Andrew N
- Stowe J
- Kirsebom F
- et al.
,
- Lopez Bernal J
- Andrew N
- gower c
- et al.
,
- Andrew N
- Tessier E
- Stowe J
- et al.
,
- Stowe J
- Andrew N
- Kirsebom F
- et al.
Our analysis included all vaccines used in the UK. Vaccination status was included as an independent variable and efficacy was defined as 1 minus vaccination probability in cases divided by vaccination probability in controls (Appendix pp. 1-3).
amountVaccine efficacy against symptomatic illness (A) and hospitalization (B) following infection with Omicron sublineages BA.1 and BA.2 in adults 18 years and older in England
- Andrew N
- Stowe J
- Kirsebom F
- et al.
,
- Andrew N
- Tessier E
- Stowe J
- et al.
,
COVID-19 Vaccine Surveillance Report: Week 7.
,
- chemaitelly h
- Tang P
- Hasan MR
- et al.
but there was no difference in the rate of decrease between the two sublines. Due to the small number of people with BA.2, we could not stratify by manufacturer in these analyses; However, in previous analyzes of the Omicron variant, after a third dose, we found little difference across vaccines.
- Andrew N
- Stowe J
- Kirsebom F
- et al.
These results are consistent with neutralization assays,
SARS-CoV-2 variants of concern and variants studied in England: technical briefing 36.
However, there is a discrepancy with a Danish household transmission study which found that BA.2 was associated with increased susceptibility to infection in vaccinated individuals.
- Lyngse FP
- Kirkeby CT
- Denwood M
- et al.
Differences between the British and Danish studies could be explained by different vaccination and infection histories in the respective countries or by methodological differences and need further investigation.
COVID-19 Vaccine Surveillance Report: Week 7.
Since the omicron variant became dominant, people have become increasingly more likely to have COVID-19 as an incidental finding rather than as the main reason for admission.
- Stowe J
- Andrew N
- Kirsebom F
- et al.
Using specific definitions to identify admissions with severe respiratory disease gives higher estimates of vaccine efficacy than using broader definitions, and these estimates likely reflect the actual vaccine efficacy in hospital admissions.
- Stowe J
- Andrew N
- Kirsebom F
- et al.
Vaccine efficacy against hospitalization was similar for BA.1 and BA.2 after the booster dose, although BA.2 vaccine efficacy may decline more rapidly than BA.1. The BA.2 analysis may be more prone to misclassification bias due to cases accidentally hospitalized with COVID-19 due to higher infection rates in the post-booster periods when BA.2 was prevalent (Appendix p. 4); This bias could explain the lower estimates of vaccine efficacy for BA.2 than for BA.1 during these periods.
We declare no competing interests. The UK Health Security Agency has statutory permission under Regulation 3 of the Health Service (Control of Patient Information) Regulations 2002 to process confidential patient information for the national surveillance of communicable diseases and therefore individual patient consent is not required to access the records.
supplementary material
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DOI: https://doi.org/10.1016/S1473-3099(22)00309-7
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