Topline
Although vaccination is still the best method to protect against the Delta variant, preliminary research by scientists at Oxford has shown that the shots are less effective against infection. The shots also lose effectiveness quickly in the months after vaccination. This adds weight to the need to administer booster shots, even though many countries have just started their vaccination campaigns.
Close-up of a young doctor wearing a blue protective glove, holding a vial getty and a medical syringe.
The Key Facts
The effectiveness of shots by AstraZeneca and Pfizer against the alpha and the delta variants was compared using test results from almost 750,000 households in the U.K.'s Covid-19 household infected survey. Although the vaccines were effective against Covid-19, the research, which is yet to be published or peer-reviewed, showed that they were less effective against the Delta variant. Researchers wrote that the Moderna vaccine was the most effective against the delta variant after just one shot. However, the group suggested that the low average age of the recipients may have contributed to this finding. It was impossible to assess two Moderna shots in detail. Researchers found that the Pfizer shot initially proved to be more effective than the AstraZeneca vaccination, but this protection waned quickly after vaccination, and within four to five months it was equal to the AstraZeneca's more stable level. The researchers stated that even though the protection provided by Covid-19 has declined, it is still the best way to protect yourself. They also said that two doses of vaccine against Covid-19 are at least as effective as natural infection.
Tangent
The study showed that people who have been fully vaccinated against the Delta Covid-19 variant of the coronavirus still have the same level of coronavirus levels as those who are not vaccinated. The researchers believe this is consistent with previous research. It could make it difficult to achieve herd immunity for emerging variants. It could be that vaccinated individuals can transmit the virus to others just as easily if they have the same amount of virus as those who are not vaccinated.
Important Quote
We are seeing real-world data of the performance of two vaccines rather than clinical trials data. The data sets all show that the Delta variant has reduced the effectiveness of both AstraZeneca and Pfizer jabs. Dr. Simon Clarke is an associate professor in cell microbiology at University of Reading. He said that the Pfizer shot's drop in immunity supports the need for third booster jabs for those most vulnerable.
Important Background
These findings confirm previous research that showed deltas can evade vaccine protection. They also add to the growing evidence that fully vaccinated individuals could transmit the delta variant as easily as those who are not vaccinated. The findings of weakening immunity, particularly in the Pfizer shot, will support booster shots being offered in rich countries. Health organizations have criticised the U.S. plan to offer them starting September. This decision has been called unfair and could prolong the pandemic. Many countries have not administered vaccines in a long time.
Continue reading
The Oxford Study examines the impact of Delta on virus burden and vaccine effectiveness for new SARS-CoV-2 infection in the UK (Oxford Study).
What is the effectiveness of Covid-19 vaccines in protecting against the Delta Variant? (Forbes)
Fully vaccinated Half as likely to catch Delta Covid Variant and Less Likely to Infect Others, Study finds (Forbes).
Johnson & Johnson Vaccine is Far Less Effective Against Delta Variant. Study suggests (Forbes).
Fully vaccinated may transmit Delta just as easily
Is it possible that vaccines are becoming less effective in preventing Covid infection? (FT)
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