Just one shot of Pfizer or AstraZeneca vaccine offers over 90% protection against COVID-19

Experts also say that Oxford-AstraZeneca vaccine work better if a gap of up to a three-month is kept between the two required doses. In India, the second dose of the vaccine is administered between four and six weeks after the first dose.

Oxford-AstraZeneca vaccine is one of the two vaccines approved for emergency use in India, the other being Bharat Biotech's COVAXIN. Under the ongoing vaccination drive, the beneficiaries are given two doses of either of the vaccine to protect them from the novel coronavirus. But new study results have revealed that just one shot of the Oxford-AstraZeneca vaccine can provide more than 90 per cent protection against COVID-19 and reduce the risk of being hospitalised due to the disease. Another vaccine developed by American drug company Pfizer showed similar results.

Compared to the Pfizer vaccine, the Oxford-AstraZeneca vaccine proved slightly more effective at preventing recipients becoming seriously ill from COVID-19, Daily Mail reported, citing the new findings. Public health officials have informed Ministers in the UK about the remarkable results of the two vaccines, the report added.

This could be the reason why lesser number of older people are being hospitalised with COVID-19 these days in the UK. According to the Daily Mail report, deaths among the over-75s have dropped by 40 per cent, while the number of over-85s being admitted to ICUs with Covid has dropped close to zero in the country.

Notably, the United Kingdom was the first country in the world to roll out the Pfizer/ BioNTech vaccine as well as Oxford/AstraZeneca vaccine. UK started vaccinating its people with the Pfizer vaccine on December 8, 2020 and Oxford/AstraZeneca vaccine in the first week of January 2021.

Longer gap between two doses makes vaccine more effective

The efficacy of the one-dose vaccination was calculated by comparing Covid hospitalisation rates in those who have received a first dose of vaccine, to those of a similar age who haven't.

Last week, a Scottish study of Covid hospitalisation rates had shown similar results. Edinburgh University researchers found that the Pfizer and Oxford-AstraZeneca vaccines can reduce the risk of hospitalisation from COVID-19 by up to 85 per cent and 94 per cent, respectively by the fourth week after the first dose.

The Oxford-AstraZeneca vaccine is being manufactured locally by the Serum Institute of India under the brand name Covishield. In studies, the vaccine has shown efficacy against the UK variant of the coronavirus, also called the B.1.1.7 Kent' coronavirus strain. But a small-scale trial of the vaccine's efficacy in South Africa showed that it offers as little as 10 per cent protection against the Covid variant first seen in country. In view of this trial results, South Africa halted the rollout of the Oxford/AstraZeneca jab.

However, the World Health Organization still recommends using the Oxford -AstraZeneca vaccine even in countries tackling new coronavirus variants. The Longer gap between two doses, as it's done in the UK, makes the vaccine more effective, WHO said. In the UK, a second dose of the vaccine is administered three months after the first shot.

Results of an Oxford Vaccine Trial also found that the vaccine work better if a gap of up to a three-month is kept between the two required doses. In India, the second dose of the Oxford/AstraZeneca vaccine is administered between four and six weeks after the first dose.