Study finds jabs cut severe variant COVID disease after one shot

A real-world study carried out in Canada has found that COVID-19 vaccines from AstraZeneca, Pfizer/BioNTech and Moderna reduce the chances of being hospitalised or dying from variants of concern dramatically, even after a single dose.

AstraZeneca's Vaxzevria was found to 87% effective against the delta variant, which is now thought to be one of the most infectious of respiratory diseases with cases surging in many countries including the US, with Pfizer/BioNTech and Moderna coming in at 78% and 96%, respectively.

One shot of Vaxzevria was also found to be 82% effective at preventing severe disease or death against the beta/gamma variant – an encouraging report given ongoing speculation that beta may be more likely to evade the immune response generated by current COVID-19 vaccines.

A study in South Africa, where the beta variant was first identified, had previously shown that Vaxzevria had little activity in preventing mild cases of this strain of SARS-CoV-2, and that was backed up in the latest study, which found a protective efficacy of only 50%.

AZ said that earlier study by researchers at the University of Oxford and University of the Witwatersrand was unable to gauge the vaccine's efficacy against severe disease because it enrolled mainly young, healthy adults who experienced mild disease only.

The World Health Organization (WHO) has said beta might be associated with higher in-hospital mortality, which was backed up by another Canadian study published earlier this month that found higher rates of transmission, hospitalisation and mortality with the alpha, beta and gamma variants.

The real-world evidence from almost 70,000 people in Canada's vaccination programme also found that Vaxzevria was 90% effective at preventing hospitalisation or death in cases infected with the alpha or UK variant, which seems now to be in decline, after a single dose.

"With different variants threatening to disrupt our route out of the pandemic, this real-world evidence shows that Vaxzevria, along with other vaccines used in Canada, provides a high level of protection against the most serious forms of the disease, even after just one shot," commented AZ's head of biopharma R&D Mene Pangalos.

"It is essential that we continue to protect as many people as possible in all corners of the world in order to get ahead of this deadly virus," he added.

Last month, AZ and Oxford University started dosing patients in a phase 2/3 trial of a new version of their COVID-19 vaccine that is designed to target the beta variant, and the UK government is looking at ordering supplies of the new version if effective to use in booster campaigns.

The UK government said that anyone entering the country from France would have to quarantine even if they were fully vaccinated, because it was concerned about the levels of beta circulating there.

France has downplayed the concerns, saying most cases of the beta variant are in its overseas territories of La Reunion and Mayotte, and earlier this week suggested levels overall are in decline.