COVID booster halved severe illness, but some groups still at higher riskA study of 30 million people in the United Kingdom finds that 0.4% of people who completed their primary COVID-19 vaccine series had severe breakthrough infections, compared with 0.2% of booster recipients, during Omicron variant predominance.The study, published today in The Lancet, also shows that older adults, men, people with underlying medical conditions, and those with suppressed immunity were remained at elevated risk for hospitalization and death after receiving the booster.University of St.
Andrews researchers in Scotland led the study of 16,208,600 people who completed their primary COVID-19 vaccination series with the Pfizer/BioNTech or AstraZeneca/Oxford vaccines from Dec 8, 2020, to Feb 28, 2022, and 13,836,390 who received a Pfizer or Moderna booster from Dec 20, 2021, to Feb 28, 2022.
Participants lived in England, Northern Ireland, Scotland, and Wales.A total of 0.4% of primary vaccine recipients and 0.2% of those who received a booster had severe COVID-19 outcomes from Dec 20, 2021, through February 2022, with booster-associated risk falling from 8.8 to 7.6 events per 1,000 person-years compared with people who didn't receive boosters.The risk of severe outcomes remained elevated in older adults (absolute risk reduction [aRR] for 80 years or older vs18 to 49 years, 3.60), those with chronic conditions (aRR for 5 or more vs no comorbidities, 9.51), men (aRR, 1.23), those taking immunosuppressant drugs (aRR, 5.80), and those with chronic kidney disease (aRR for stage 5, 3.71).
Previously COVID-infected people were at lower risk (aRR for infected at least 9 months before booster, 0.41).The at-risk groups should "be prioritised for