Category: Good News

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

Disclaimer: Please note- This blog is NOT medical advice. This blog is NOT a expert medical opinion on various topics. This blog is purely for information only and do check the sources where cited. Please DO consult your own doctor to discuss concerns and options relevant to you. The views expressed in this blog represent the author’s views held at the time of drafting the blog and may change overtime, particularly when new evidence comes to light. The blog is not previewed, commissioned or otherwise endorsed by any organisation the author is associated with. The views expressed in this blog are not in way intended to be a substitute for professional advice.

Can someone die due to COVID-19 infection even after having the full course of protective vaccination?

Yes, rarely it can happen.

COVID vaccines are very highly effective in preventing serious infections that would result in hospitalisation. Even a single dose of the vaccine has very good efficacy.

But vaccines are not 100% effective.

So until the pandemic is under full control, older adults, particularly those over 60 years, should be cautious even after full vaccination.

It also has to be said that the risk is dramatically small after full vaccination. Only a tiny minority of people get serious COVID-19 infection after full vaccination.

In USA, about 5800 “breakthrough” COVID-19 infections has been reported so far among the roughly 77 million people who had been fully vaccinated. That’s less than 0.008% cases.

A much more smaller minority among this minority group had serious infections. Among the 5800 cases, 396 patients were admitted to hospital and 74 patients died from COVID-19. That’s less than 0.0001% deaths.

So unless new viral mutations dramatically reduce vaccine efficacy, it looks very promising.

References:

1. BMJ News. Covid-19: Infections fell by 65% after first dose of AstraZeneca or Pfizer vaccine, data show BMJ 2021; 373 doi: https://doi.org/10.1136/bmj.n1068 (Published 23 April 2021)
Cite this as: BMJ 2021;373:n1068

2. BMJ news. Covid-19: US reports low rate of new infections in people already vaccinated
BMJ 2021; 373 doi: https://doi.org/10.1136/bmj.n1000 (Published 16 April 2021)
Cite this as: BMJ 2021;373:n1000

3. Sun News. DOUBLE TROUBLE ‘Concerning’ Indian Covid variant now in UK has two ‘escape mutations’ that could dodge antibodies
Vanessa Chalmers, Digital Health Reporter
12:22, 16 Apr 2021Updated: 12:25, 16 Apr 2021

4. BBC news. Coronavirus: ‘Double mutant’ Covid variant found in India. Published 25 March

5. Daily Mail. Could the Indian ‘double mutant’ coronavirus derail Britain’s roadmap out of lockdown? Experts warn variant could ‘scupper our escape plan’ and urge Boris to put country on red list. By James Robinson for MailOnline
01:49, 17 Apr 2021 , updated 11:08, 17 Apr 2021

Disclaimer: Please note- This blog is NOT medical advice. This blog is NOT a expert medical opinion on various topics. This blog is purely for information only and do check the the sources where cited. Please DO consult your own doctor to discuss concerns and options relevant to you. The views expressed in this blog represent the author’s views held at the time of drafting the blog and may change overtime, particularly when new evidence comes to light. The blog is not previewed, commissioned or otherwise endorsed by any organisation the author is associated with. The views expressed in this blog are not in way intended to be a substitute for professional advice.