Top health expert thinks Pakistan rapidly moving towards COVID-19 herd-immunity

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By the first week of September 2020, around 65-70% of Karachi’s population would be carrying COVID-19 antibodies as the country is moving towards herd-immunity within the next two months, claimed a top Pakistani health expert, Dr Tahir Sultan Shamsi.

The doctor said that in the third week of July this year, almost 40% of the city’s population had been exposed to the virus infection and this number will expand by September.

Dr Tahir said: “Our research on three different segments of the society reveals that around 40% of Karachiites have so far been infected with the coronavirus asymptomatically and by the first week of September 2020, 65-70% of city’s population would have been infected with the virus, which is a minimum requirement for achieving herd immunity in the COVID-19 case.”

The hematologist gave the example of neighbouring India, where he said that less than 1% of the population has tested positive, but a survey by the Indian government has revealed that one in four persons have already been exposed to the virus in New Delhi. 

“In Karachi, based on antibody tests conducted by us at the National Institute of Blood Diseases (NIBD), Karachi, through five different FDA-approved kits and methods indicate that around 40% of the city’s population has already contracted coronavirus infection asymptomatically,” Dr. Shamsi said.

“We expect that by the first week of September 2020, around 65-70% population in Karachi would be carrying COVID-19 antibodies, which is required for herd immunity in a population,” he added.

The hematologist said that the results are not a population-based study as was the case in the idea. The doctor said that the results from three different sets of people, including industrial workers, healthy blood donors, and healthcare workers, indicate that around 40% of Karachi’s population has already “contracted” the disease without having knowledge of it and the results can be seen from the declining number of the coronavirus cases in July.

“In April, only 5% of people tested had developed COVID-19 antibodies, in May it reached 12% and in June 21% people from three different segments of the society were seropositive. The ratio is around 40% in the third week of July 2020," Prof. Shamsi said adding that Anti-SARS-CoV-2 antibody tests were done on Roche Kits on workers of media houses, industry, healthcare workers and healthy blood donors.

“Sample size was 700-800 in each group respectively. We used the first generation kits and tested these people through five different FDA approved methods. Our results indicated that chances of false-positive were very low as compared to false-negative results," Dr. Shamsi added.

“We did the maximum work on COVID-19 antibodies in the last four months, from qualitative testing to quantitative analysis of COVID antibodies. No other institution has done any comparative work. Because of our major research on convalescent plasma, we had to do all the specialized tests," he said.

Dr Shami asked the authorities in Karachi to conduct a population-based sero-surveillance study in Pakistan as it can assess the actual infected people in the country.

“All parameters in Pakistan are indicating that we are heading towards herd immunity, which is evident from a dramatic decrease in COVID-19 cases in the last 8-10 days," Prof. Shamsi said.

‘Significant overestimation’

Epidemiologist Dr. Rana Muhammad Safdar called the remarks by Dr Shamsi, a “significant overestimation” and said that they cast doubt on the quality of screening tests.

“I am not very confident if the newly-used tests correctly detect COVID-19 antibodies or cross-react with other preexisting ones as well," he said in contradiction.

When asked if the National Health Services Academy has started a WHO-supported sero-surveillance in a sample of 6,000 population, he said the survey has not started yet.

Health expert PM’s focal person on COVID-19, Dr. Faisal Sultan said Dr. Tahir’s claim is based on a “single-source data”, which is fine but one should exercise caution with the extrapolations.

"Let the serosurvey come in and we will know the accurate percentage of people who have contracted the disease in Pakistan," he said adding that there is a global collaboration for the nation-wide serosurvey in Pakistan.

“Despite its limitations, it needs to be done. The main issue is interpretation with knowledge,” he concluded.

Originally published in The News