I am an immunologist and have worked on T-cells half my life. In this thread I will present a rebuttal that will hopefully encourage more debate.

The idea that herd immunity can be achieved by 10-20% infected/vaccinated people is itself wrong and deeply flawed. 1/n https://twitter.com/JamesTodaroMD/status/1292873236716433416

2/n If 10% people have protective immunity, how can they protect rest 90%? Statistical analysis shows that when ~ 70% people are immune, the probability of getting the disease in a given community plummets but still is not foolproof.

Dangerous to assume otherwise.

3/n Yes, previous corona exposure will generate T cell response But (i) how many are previously infected? (ii) Are there cross reactive T cells/common antigen? (iii) If so what is their antigen specificity? (iv) NO evidence thus far that "past-corona" T cells are protective now.

4/n Mumbai shows 50% population have antibodies. But if herd immunity achieved is by only 10-20% immune population, we should have seen only few or none having the disease. In reality, positive cases are shooting up massively.

5/n Similarly in Delhi, 23% population has antibodies. By the way, those who have antibodies will also have T cells, at least Th (CD4+) cells.

Also, in almost every case of viral infection where antibodies are produced, cytotoxic T (Tc) cells are also induced!

6/n Cell paper claims 40-60% popln have T cells that are cross reactive to SARS-CoV-2. ANY evidence these T cells are protective? NO.

Even if you say they are protective, they may protect these individuals. But where is the herd immunity? CoVID continues to infect, cause havoc.

7/n I presume you are referring PCR positive cases. Argument doesn't hold. If these people had the "vaccine effect", one would not have seen any virus. These people would have shown antibodies/ T cell responses but not live virus. https://twitter.com/JamesTodaroMD/status/1292873244236820481?s=20

8/n I lived in New York for 13 yrs, flu seasons affected everyone. If common cold "corona" immunity would have protected, NY wouldn't be so hard hit.

Heath care systems, discipline, population density helped Sweden and NOT ~20% infection-achieved herd immunity.

9/9 Remember - Those having antibodies also have T cells, at least Th (CD4+) cells and in almost every case of viral infection where antibodies are produced cytotoxic T (Tc) cells are also induced.

If 20% have antibody immunity, it DOESN'T mean that 50-60% have T-cell immunity!