Pfizer jab shows its calibre in fifth wave, Discovery analysis shows
Preliminary analysis suggests the shot held up against the Omicron sub-lineages BA.4 and BA.5
Pfizer-BioNTech’s Covid-19 vaccine provided strong protection against hospitalisation during SA’s fifth wave of coronavirus infections, suggesting the shot held up against the Omicron sub-lineages BA.4 and BA.5. This is according to preliminary analysis from health and life insurer Discovery.
The real-world study, which has yet to be published, drew on data from 1.58-million Gauteng-based beneficiaries of medical schemes administered by Discovery Health between April 1 and mid-May, when SA experienced its fifth surge in coronavirus cases.
Discovery Health is a subsidiary of the JSE-listed Discovery, and has access to claims data from the 3.3-million beneficiaries of its 19 client medical schemes.
The finding is important because previous laboratory analysis has found the antibodies generated by the Pfizer vaccine have a reduced ability to neutralise Omicron compared with older variants such as Delta.
People who had received two doses of the Pfizer jab had an 87% lower risk of hospitalisation after infection with the virus than people who had not been vaccinated, two months after they got their second shot.
Vaccine efficacy against admission to hospital dropped to 84% at between three and four months and fell to 63% at five to six months.
These two-dose findings are comparable with previous analysis of vaccine efficacy against the earlier Omicron strains, BA.1 and BA.2, which drove SA’s fourth wave in December.
The latest study also looked at the impact of Pfizer booster shots and found vaccine efficacy against hospitalisation leapt to 88% three to four months after people received their third dose.
“What is unique here is that it is the first glimpse of vaccine efficacy against BA.4 and BA.5. (The analysis) shows there is continued vaccine efficacy against these variants and, most importantly, three doses have a higher lift in terms of protection than two,” said Shirley Collie, Discovery Health’s chief healthcare analytics actuary.
Discovery’s data shows a continued decoupling of cases and admissions to hospital during the fifth wave, maintaining the trend first observed in December. The total number of hospital admissions for severe Covid-19 during the study period was 718, said Collie.
Discovery previously co-authored a study with the Medical Research Council, published in the New England Journal of Medicine that compared the vaccine effectiveness of the Pfizer jab to Johnson & Johnson’s shot between November 15 and December 7.
It found people who had received two Pfizer doses were 70% less likely to be hospitalised than unvaccinated people one to two months after their second shot, while those who received two J&J doses were 72% less likely to be hospitalised.
Collie said it was too soon to tell from Discovery’s data whether there was a significant waning of protection after a third Pfizer shot.
SA began offering boosters to adults at the end of December, but take up has been relatively slow, with only 3.26-million administered to date. A total of 19.74-million adults have received at least one shot, equivalent to 49.8% of Stats SA’s 2021 mid-year population estimate of 40.1-million adults.
On Monday, the government began providing a second booster to people over the age of 50.
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