The Pfizer and AstraZeneca COVID-19 vaccines are highly effective against the variant first found in India, but only if you get both doses, real-world data shows

  • Pfizer and AstraZeneca’s COVID-19 vaccines work against variants first found in India, real-world data shows.
  • Pfizer’s vaccine was 88% effective after two doses and AstraZeneca’s was 60% effective against the variant, a UK study found.
  • A single dose of Pfizer or AstraZeneca’s vaccine was 33% effective, highlighting the importance of a second shot.
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Pfizer and AstraZeneca’s COVID-19 vaccines are highly effective against the variant first found in India, which has fueled record-breaking infection numbers in the country and overwhelmed its healthcare system, new real-world data shows.

The UK-based study, from England’s public-health authority, found that two doses of Pfizer’s vaccine was 88% effective at preventing symptomatic COVID-19 caused by the variant first found in India, which is called B.1.617.2. Two doses of AstraZeneca’s vaccine was 60% effective, the study found. 

The UK has reported more than 4,000 cases of the variant, which has now spread to 49 countries including the US, according to Global Initiative on Sharing Avian Influenza Data. B.1.1.7, the variant first identified in the UK, remains the most common variant in both countries.

One dose offered far less protection, the Public Health England (PHE) study showed. A single dose of either vaccine was 33% effective against COVID-19 with symptoms caused by B.1.617.2. 

The study, which was posted as a preprint Saturday and is yet to be peer-reviewed by other experts, is the first in the world to show that vaccines offer some protection against B.1.617.2, which has mutations that make it highly infectious and potentially able to escape antibodies produced by vaccines.

For comparison, two doses of Pfizer’s vaccine was 93% effective against symptomatic COVID-19 caused by the most common variant in the US, B.1.1.7, and AstraZeneca’s was 66% effective. After one dose, both vaccines were 50% effective against B.1.1.7, the data showed. 

Matt Hancock, the UK’s health and social care secretary, said Sunday in a press release that the findings were “groundbreaking” and showed the importance of getting a second dose to secure the “strongest possible protection” against coronavirus variants. 

Second shot of Pfizer and AstraZeneca boosted protection

The PHE study adds to a growing body of real-world evidence that one dose of COVID-19 vaccines provide some protection against coronavirus, and that protection is boosted by the second dose. PHE’s most recent surveillance report, for example, said that a single dose of either Pfizer’s or AstraZeneca’s vaccine was between 55% and 70% effective, rising to between 85% and 90% after two doses. 

Adam Kucharski, associate professor at the London School of Hygiene and Tropical Medicine, said on Twitter Sunday that “first and foremost” the study was “another reminder that second doses matter.”

The actual amount of protection offered by the vaccines could be more than it seems from the figures, as the PHE researchers did not look at whether the vaccines protected against severe disease caused by variants. COVID-19 vaccines typically offer more protection against these outcomes. 

The lower efficacy of AstraZeneca’s vaccine after two doses, compared with Pfizer’s, could be down to the fact that it was mostly given to older people, who have weaker immune responses, the study’s authors said.

Other data has shown that AstraZeneca’s vaccine can take longer than Pfizer’s to reach maximum effectiveness after the second dose.

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