Two doses of the Pfizer-BioNTech vaccine for COVID-19 are 90% effective against hospitalisation due to all variants for at least six months, according to the latest analysis.
The study was carried out by researchers from Kaiser Permanente and Pfizer. They analysed 3,436,957 electronic health records from the Kaiser Permanente Southern California health system.
Information was extracted on COVID-19 infections, hospitalisations and deaths between December 2020 and August 2021.
Among the participants, 5.4% had a confirmed case of COVID-19, of whom 6.6% needed hospitalisation. Infection took place between three to four months after their second jab, on average.
Protection against infection waned from 88% within a month after the second dose to 47% after six months. However, effectiveness against hospitalisation for all variants – including delta – was still at 90% after six months, the researchers report.
Findings appeared in the Lancet. Dr Luis Jodar, Senior Vice Lead author, Dr Sara Tartof of Kaiser Permanente in Southern California, USA, explains that these findings are consistent with early reports from the US Centers for Disease Control and Prevention and the Israel Ministry of Health.
She said: “Our study confirms that vaccines are a critical tool for controlling the pandemic and remain highly effective in preventing severe disease and hospitalisation, including from the delta and other variants of concern."
On the subject of booster shots, she added: "In line with the recent Food and Drug Association and Centres for Disease Control and Prevention recommendations, considerations for booster shots should take global COVID-19 vaccine supply into account as people in many countries around the world have not yet received a primary vaccination series.”
Tartof, S. Y. et al. Effectiveness of mRNA BNT162b2 COVID-19 vaccine up to 6 months in a large integrated health system in the USA: a retrospective cohort study. Lancet 4 October 2021; doi: 10.1016/S0140-6736(21)02183-8
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