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Why Has The Efficacy Of COVID-19 Vaccines Dropped?

By Dr. Nikita Toshi +2 more

The debate surrounding the COVID-19 vaccines seems to be never-ending. During the first outbreak last year there was much hype and concern on whether we will ever have a vaccine in time to put a stop to the spread given the unknown nature of the novel virus. Once that question was put to an end with an array of vaccines (Pfizer-BioNTech, Modern, Oxford-AstraZeneca, Covaxin, Sputnik V, Johnson & Johnson’s Janssen) being released into the market worldwide, there was another matter of concern and controversy; does taking the vaccine put your life at risk? This subsequently led to a significant degree of vaccine hesitancy amongst the older as well as the younger generation causing a delay in the vaccination drive.

Upon successful assurance and expedition of the drive, now there is another disheartening revelation – COVID vaccine efficacy seems to be dropping down.

This fact became evident when about two months ago (in July) Israel recorded a steep decline in the efficacy rate of their inoculated Pfizer-BioNTech vaccine. Ynet News reported that the COVID vaccine efficacy had dropped down to a startling 60% from June as it was failing to curtail the infection rates in the face of the Delta variant wave and the associated easing of COVID restrictions. 

Why is it Dropping? 

As per reports published in The New England Journal of Medicine, researchers monitored how the effectiveness of the vaccine dropped to 96% between May June and then to about 60% in July. Researchers as well as doctors after careful consideration of the situation came to three possible conclusions. 

  1. The immune response to mRNA based vaccines starts to dwindle over time. Longer the gap from the time when you have first vaccinated the faster the decline in neutralizing antibodies your immunity might have had. This means that with a compromised COVID immunity the efficacy of the vaccine is also lowered.
  1. Another point that determines the vaccine effectiveness is the surrounding infection rate. If the infection spread in your community is extremely high, your vaccine will not be able to protect you 100%. So masking up and maintaining social distancing still stands as the standard COVID-19 safety protocols no matter if you are vaccinated or not. 
  1. The third factor pointed out by doctors is that your vaccine efficacy will alter depending on the type of infection raging in your community at a given time. A contagious delta variant infects people aggressively therefore a variation in efficacy can be seen.

Do booster shots actually help? 

As per the current trend, fully inoculated people are getting infected with a percentage in some places as worrisome as 50%. The COVID-19 virus is constantly evolving and coming back stronger in each wave. So, in order to really take things up a notch and boost up our immunity doctors are saying that booster shots might be the need of the hour. But how do these shots work?

A vaccine is made up of inactive or weakened viruses or bacteria. When you get yourself the booster dose it prepares your immunity to combat the foreign invasion in the same way as it would for the original infection. This aids your body to create a memory of the virus. If you are exposed to the virus or bacteria again the antibody will be able to detect and finish it off before it can bring about severe damage. You can get booster shots a few weeks, months or even years after your vaccine shot depending upon the guidelines issued in your country.

However, the current government focus in India is to complete the vaccination of the Indian population as that was most necessary. Although many western countries are emphasizing the need for a booster shot drive right away, the Indian Council of Medical Research (ICMR) is only concerned with getting as many adults vaccinated as possible. So, though a booster shot might be effective in giving your better protection against future COVID-19 infections it is not the agenda of the Health Ministry as of this moment.  

Also Read: Omicron Variant & Vaccine Efficacy


Although the majority of COVID-19 hospitalization cases have been seen amongst unvaccinated people (especially during the Second Wave in India), there is no guarantee how strong the next viral strain might be and to what extent the vaccine can shield you from possible future infection. Additionally, with the drop in COVID vaccine efficacy over time, the need for booster shots might be essential eventually to not only keep your immunity strong against further COVID-19 infections. A complete vaccination does protect you from getting severely infected but it may not be able to provide you 100% safety from re-infection. Therefore it is important to get vaccinated and also follow COVID-appropriate behaviour for your own safety and the safety of others.

Also Read: Omicron Variant: Latest News & Updates

Disclaimer: The information provided here is for educational/awareness purposes only and is not intended to be a substitute for medical treatment by a healthcare professional and should not be relied upon to diagnose or treat any medical condition. The reader should consult a registered medical practitioner to determine the appropriateness of the information and before consuming any medication. PharmEasy does not provide any guarantee or warranty (express or implied) regarding the accuracy, adequacy, completeness, legality, reliability or usefulness of the information; and disclaims any liability arising thereof.

Links and product recommendations in the information provided here are advertisements of third-party products available on the website. PharmEasy does not make any representation on the accuracy or suitability of such products/services. Advertisements do not influence the editorial decisions or content. The information in this blog is subject to change without notice. The authors and administrators reserve the right to modify, add, or remove content without notification. It is your responsibility to review this disclaimer regularly for any changes.


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