Covid-19 vaccine may have significantly cut deaths among elderly despite spread of new strain, Brazil research shows
- Scientists estimate that that vaccines may have prevented 14,000 deaths among over-80s despite the emergence of a new coronavirus variant
- Most of those in the study had been given a drug made by the Chinese company Sinovac
A rapid roll-out of Covid-19 vaccinations among elderly Brazilians may have significantly reduced deaths even though a new variant of the virus was spreading, new research has found.
The vaccines may have prevented 14,000 deaths among over-80s, according to estimates by researchers at Harvard’s TH Chan School of Public Health and Brazil’s Federal University of Pelotas.
The new study published on the preprint site MedRxiv.org, which has not yet been peer-reviewed, comes as many countries are battling new Covid-19 surges and as scientists are racing to gauge the real-world impact of vaccines.
The vaccine’s efficacy rate of 50.7 in a Brazilian clinical trial only narrowly passed the WHO requirements for preventing symptomatic Covid-19.
But experts say the vaccine’s role in fighting Covid-19 is also linked to how well it can prevent serious disease and death, especially among older adults who are more vulnerable to the disease.
The latest study in Brazil analysed 171,454 deaths linked to Covid-19 from the start of the year through to mid-April.
The researchers found that in January the mortality rate for over-90s was 20 times that of people under 79. But that ratio started to decline in February amid a vaccination drive.
By April the over-90s mortality rate was eight times that of under-79s.
A similar phenomenon was observed among over-80s, with the comparative mortality rate cut by nearly half.
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The findings coincided with a robust vaccination campaign targeting the elderly, where over 90 per cent of over-80s had received at least one dose by mid-March, the researchers said. Sinovac’s Coronavac has accounted for 77 per cent of vaccinations, compared with a 16 per cent using an AstraZeneca vaccine.
Both vaccines require a two-dose regime.
Around half of the population had received two doses of the Sinovac vaccine by the end of the study, meaning a significant proportion were not yet fully protected.
“We found evidence that, although dissemination of the P1 variant led to increases in reported Covid-19 death at all ages, the proportion of deaths among the elderly started to fall rapidly from the second half of February,” the researchers said.
“The most likely explanation … is the rapid increase in immunisation coverage in these age groups.”
They noted some limitations to the research. For example, if the variant disproportionately affected younger groups this could skew results.
The data follows a real-world study by the Chilean government covering 11 million people. It found deaths related to Covid-19 rose at a significantly lower rate among people who had been vaccinated, most of whom had received Sinovac’s product
Researchers estimated 14 days after the second dose the jab was 80 per cent effective at preventing death.
Such trends have been observed in other contexts around the world.
In the United States, where nursing home residents were among the first to receive vaccines made by Moderna or Pfizer-BioNTech, there was a significant decrease in deaths in this group, even as they rose in the general population.
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Real-world data from a study in two British hospitals that showed the AstraZenca vaccine helped prevent hospitalisations among over-80s also helped increase confidence in the vaccine by filling in gaps in the available data.
An assessment released last week said that a WHO expert group had “moderate” confidence that the Sinovac vaccine was efficacious in adults over 60 based on the available data.