The latest scientific studies on the efficacy of Covid-19 vaccines and how inoculation mitigates the effects of the virus have shed more light on the disease and its prevention.
Source: Reuters reported on Aug. 10 that two papers that have not been peer reviewed were posted on medRxiv -- a health sciences publishing platform -- on Sunday, Aug. 8.
Findings: The papers described studies that showed the mRNA vaccine from Moderna is likely to be more effective than the one from Pfizer/ BioNTech against the Covid-19 Delta variant.
A third paper traced the effectiveness of the Pfizer vaccine over time in one country's population.
First paper
Moderna's effectives: Researchers found the effectiveness of Moderna's vaccine against infection had dropped from 86 per cent in early 2021 to 76 per cent in July, in a study of more than 50,000 patients in the Mayo Clinic Health System.
Mid-2021 was when the Delta variant was predominant.
Pfizer's effectives: On the other hand, the effectiveness of the Pfizer/ BioNTech vaccine had fallen from 76 per cent to 42 per cent over the same period.
What it means: The overall drop in effectiveness indicate a Moderna booster shot may be necessary soon for anyone who got the Pfizer or Moderna vaccines earlier in 2021 as inoculation might be wearing off.
But both vaccines remain effective at preventing Covid-19 hospitalisation.
Second paper
Moderna produced stronger immune responses: In a second study, elderly nursing home residents in Ontario given the Moderna vaccine produced stronger immune responses, in particular, to the more problematic variants, as compared to those who were given the Pfizer/ BioNTech vaccine.
What it means: Overall, the elderly may need higher vaccine doses, boosters, and other preventative measures.
In response to these preliminary findings, a Pfizer spokesperson told Reuters: "We continue to believe... a third dose booster may be needed within six to 12 months after full vaccination to maintain the highest levels of protection."
Pfizer's vaccine protection wears off with time
Third paper
Pfizer vaccine wears off after a few months: People who were fully vaccinated less than five months ago are less likely to test positive for Covid-19, compared to people who received their second dose of the Pfizer/ BioNTech vaccine five or more months ago.
The paper was also put up on medRxiv ahead of peer review.
The new data that researchers studied involved nearly 34,000 fully vaccinated adults in Israel.
They were tested to see if they had a breakthrough case of Covid-19.
Overall, 1.8 per cent tested positive.
What it means: At all ages, the odds of testing positive were higher when the last vaccine dose was received at least 146 days earlier.
Among patients older than 60, they were three times more likely to test positive for Covid-19 when at least 146 days had passed since the second dose.
However, the research found that very few patients had required hospitalisation.
Moreover, it is too early to assess the severity of these new infections in terms of hospital admission, need for mechanical ventilation or mortality, a co-author of the research said.
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