How effective is a single dose of Pfizer and AstraZeneca vaccine?

UK government wanted as many people have “some” degree of protection against the COVID-19 rather a only few people having “full” protection against COVID-19.

So the U.K. government delayed the second dose of Covid vaccine for 12 weeks.

Some people have now been offered two vaccines but still there are many people who were yet to have the second dose. They would be wondering how effective a single dose of the vaccine is. How much protection they have now.

A recent paper published in BMJ provides very encouraging news .

With Pfizer vaccine, vaccine effectiveness reached 61% after 4 to 5 weeks of the first dose.

With AstraZeneca vaccine, vaccine effectiveness reached 73% after 5 weeks of first dose.

This data is very reassuring

But the data also stresses the importance of having the second dose for further protection.

Please do make a note that (a) vaccines do take a few weeks to be become effective after the first dose (b) no vaccine is 100% effective and (c) we also do not know how long this protection from vaccine will last.

BMJ. Effectiveness of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines on covid-19 related symptoms, hospital admissions, and mortality in older adults in England: test negative case-control study
BMJ 2021; 373 doi: https://doi.org/10.1136/bmj.n1088 (Published 13 May 2021)
Cite this as: BMJ 2021;373:n1088

BMJ. Public health impact of delaying second dose of BNT162b2 or mRNA-1273 covid-19 vaccine: simulation agent based modeling study
BMJ 2021; 373 doi: https://doi.org/10.1136/bmj.n1087 (Published 12 May 2021)
Cite this as: BMJ 2021;373:n1087

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