Do we need a Booster Shot ?

Literature regarding vaccine efficacies are few and far between. It is now accepted that the immunity wanes over time. There are hardly any studies available about vaccines of Indian, Chinese and Russian make. An honest attempt is made to evaluate the efficacy of various combinations published in a prestigious medical journal, the Lancet.

Safety and Immunogenicity Report of COM-COV Study published in lancet on 25.6.21

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3874014

In UK, both Covishield and Pfizer vaccines are available. Immunity of people who have received a booster shot of Pfizer after 2 doses of Covishield are compared with those who have received only 2 doses of Covishield. There are a group who have received vaccine after getting infected. Both antibody level and T cell response are measured after 28 days post-Boost. I have summarised the results in the table below.

Combination	ELU/ml	Remark
Pfizer/Pfizer	14,080	Highest
Covishield/ Pfizer	12,906	Non- Inferior
Pfizer/ Covishield	7,133	GMR- 0.51
Covishield/ Covishield	1,392	Control

Antibody titre against the Spike protein in the booster series is 9 times higher than 2 doses of AZ vaccine. A booster by Pfizer and AstraZeneca vaccines are equivalent in potency

Combination	SFC/10^6 PBMC	Remark
Covishield/ Pfizer	185	Highest
Pfizer/Pfizer	80	Non- Inferior
Pfizer/ Covishield	99	Non- Inferior
Covishield/ Covishield	50	Control

T cell response in the booster series is higher than 2 doses of AZ vaccine. A booster by AZ is higher than Pfizer booster and longer lasting. ( T cell response are always better defence against intracellular pathogens like virus.)

• Immunity induced by all Covid vaccines is found to wane after 6 months. I have attempted to arrange some combinations in order from best to worst with respect to this “waning of immunity.“
  1. Covid-19 disease followed by the vaccine gives you the best protection. It Covers all prevailing variants and induces longer immunity.
  2. Astrazeneca 2 doses followed by Pfizer booster is the next best.
  3. Booster dose of Pfizer after two doses scores non inferior to above.
  4. Moderna 2 doses as licensed ranks higher than other prime series as per various antibody studies.
  5. Routine Pfizer 2 doses.
  6. Routine Astrazeneca 2 doses.

( No literature is available on other combinations till date.)

Compiled by ରମାକାନ୍ତ ମହାପାତ୍ର