Which is the best vaccine for COVID 19?
Posted on: 23/Mar/2021 11:33:44 AM
Dr D P Prakash FRCS DNB DO MBBS Ratan Tata Fellow American Eyecare & LASIK - March 24, 2021 Chennai
This is a very important question that everyone is asking now. You have to understand What you are reading in the newspaper and seeing on television or internet about vaccine efficacy .
The efficacy of Pfizer or Moderna vaccine is close to 95% whereas the covishield is only 60% according to initial studies. Does this mean that the Pfizer vaccine is superior to the COVISHIELD VACCINE?
Simple answer is NO. All vaccines are the SAME when it comes to their EFFECTIVENESS IN PROTECTION AGAINST COVID HOSPITALISATION OR DEATH FROM COVID 19.
Efficacy reports that you read in media is not the same as effectiveness. Understanding this is very very crucial for everyone. All vaccines are 100% effective against preventing COVID deaths or Hospitalisation with severe disease. Remember 98% of COVID infected patients survive without any problem. So the role of the vaccine is to protect that 2% who might die from the COVID disease. In achieving that goal ALL COVID VACCINES AVAILABLE NOW ARE 100 % EFFECTIVE.
So what is this efficacy report then? Why is it different for different vaccines even though all of these vaccines are EQUALLY 100% EFFECTIVE?
Efficacy rate is obtained from VACCINE TRIALS , not from REAL WORLD.
THE EFFICACY IS A NUMBER OF how many people who TESTED POSITIVE FOR COVID AFTER TAKING THE VACCINE versus HOW MANY TESTED POSITIVE AMONG THOSE WHO DID NOT TAKE THE VACCINE IN A GIVEN TIME... usually 60 days. Both these groups of people have been enrolled in the STUDY AND COMPARED DURING A GIVEN TIME PERIOD.
The result of this study will differ based on the following important factors
The most important being What is the number of cases of COVID cases during the time at which the study was conducted !!!
If THIS VACCINE EFFICACY study was conducted in a place where COVID infection is very negligible like NEWZEALAND , then in all likelihood there may not be anyone in both groups - those who did have the vaccine or those who did not- testing positive for COVID. Since there�s no difference between the two groups the efficacy of the vaccine will be reported as �0� zero. At the same time if 1 person who did not take vaccine tested positive and no one who took the vaccine was positive for COVID then the efficacy of the vaccine will be reported as 100%. This has no correlation to the protection that the vaccine offered in preventing death or hospital admission.
The PFIZER & MODERNA VACCINE study were conducted only in USA 🇺🇸 WHEN THE number of COVID cases were very low at 20 cases per 100,000 during August to November 2020. Comparatively The Jhonson & Jhonson vaccine trials were conducted in USA 🇺🇸 between November 2020 & February 2021 when the positivity rate was 400% higher at 80/ 100,000. This means that there was a higher risk for people to get COVID infection during this period just by chance. The same thing holds true for the COVISHIELD VACCINE too as the trials were done in different parts of the world when the case positive rates were much much higher than 20/100000 .
The important thing to note is that all the 4 vaccines prevented death or Hospitalisation due to severe COVID infection in the SAME PERCENTAGE- 100% even though the reported efficacy rates of Pfizer & Moderna was 95% and that of the J&J and Covishield vaccine was only 66%. Thus it is very clear that efficacy rates of vaccine is not the same as EFFECTIVENESS OF PROTECTION. Another important thing to understand is that efficacy rates of 2 vaccines are comparable only if the vaccine trials were conducted in the same time period and in the same country, because case prevalence affects the efficacy rates.
In conclusion ALL VACCINES ARE EQUALLY EFFECTIVE IN OFFERING YOU PROTECTION AGAINST SEVERE COVID DISEASE OR DEATH DUE TO COVID.
It�s always useful to remember that vaccine is like a helmet that protects your head from impact in an accident. But safe driving prevents an accident. Similarly A properly worn mask, social distancing and hand sanitizer prevents anyone from getting infected. It�s very prudent to PREVENT COVID 19 WITH MASK SOCIAL DISTANCING and HAND HYGIENE along with PROTECTION WITH A VACCINE. Any vaccine is better than no vaccine.
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