With input from Dr Monica Vasudev

1534: Super-spreader events are pivotal to the survival and predominance of new variants.

If the transmission of the virus only occurs one person at a time, a new variant cannot gain dominance and will die out in the population by chance.

Even strong variants can die out if they are not by chance transmitted in a super-spreader event.

Early super-spreader events that infect over five people are critical to the survival of a variant, while super-spreader events that infect over 20 people are critical to its dominance.

Even a highly infectious new variant will need a super-spreader event to help it overtake a current variant. (Reuters)

1535: Antibodies induced by the Pfizer/BioNTech and Moderna vaccines as well as the antibody therapy from Regeneron, can neutralize a coronavirus variant currently surging in New York.

The New York variant contains mutations E484K, S477N and D235G. Experts were concerned that the variant might diminish antibody efficacy. However, new results suggest that this potential problem is not a problem.

The mutations cause changes to the spike protein. The researchers exposed copies of the New York variant to blood obtained from individuals who had received either the vaccines or the antibody combination from Regeneron. Vaccine-induced antibodies were found to be highly effective at binding to the altered spike protein, and the Regeneron therapy was also a potent blocker of the virus, reported researchers. (Reuters)

1536:   Rare but serious blood clots have been reported among some individuals who have received AstraZeneca COVID-19 vaccine. They appear to be similar to heparin-induced thrombocytopenia (HIT). Here, heparin incites the immune system to produce antibodies that activate platelets. Drugs apart from heparin can lead to clotting disorders resembling HIT, and it is suspected that in rare cases, this vaccine may act as another such trigger.

Four healthy individuals who got the AstraZeneca vaccine and developed clots appeared to have the same kind of antibodies that activate platelets and initiate clotting in HIT, noted researchers in a paper posted on Research Square.

Twenty individuals who were administered the vaccine but did not develop clots were found not to have these antibodies. (Reuters)

1537: Antibodies against SARS-CoV-2 may die out at different rates based on the severity of the infection. The researchers in a new study, followed 164 COVID-19 patients for up to nine months following infection. Five distinct groups were identified based on patterns of neutralizing antibodies:

- Negative group - did not develop neutralizing antibodies at the 30% inhibition level. They comprised 12% of patients in the study.

- Rapid waning group comprised 27% of the study patients. They had varying early levels of antibodies from around 20 days of symptom onset, but they sero-reverted in less than 180 days.

- Slow waning group - 29% of the study subjects; they remained antibody-positive at 180 days following symptom onset.

- Persistent group comprising 32% of the study subjects. They had minimal antibody decline up to 180 days.

- Delayed response group comprising 2% of the subjects in the study. They had a marked increase in neutralizing antibodies during late convalescence (at 90 or 180 days after symptom onset).

In the study published in Lancet Microbe, the researchers stated that persistence of neutralizing antibodies had a link with disease severity and sustained levels of pro-inflammatory cytokines, chemokines, and growth factors. T-cell responses did not have a clear link with the different patterns of neutralizing antibodies.

(The Lancet Microbe, online March 23, 2021.)

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA