Need for second Covid booster not backed by scientific evidence: Experts

Express News Service

BENGALURU: Amid the rising number of Covid cases, some doctors and healthcare workers like nurses and pharmacists who have taken their booster doses have been stressing on the need for a second booster dose. However, some experts feel that due to the immunogenicity (ability to provoke an immune response) of the Indian vaccines and the current risk factor, there is no need for it.

Dr C N Manjunath, Director of Sri Jayadeva Institute of Cardiovascular Sciences and Research (SJICSR) who is also a member of Karnataka State’s Clinical Experts Committee, said, “I have come across many healthcare workers and doctors asking me whether they take should take the fourth vaccine as they are constantly exposed to patients on a daily basis. The recent surge in Covid cases abroad has fuelled this question. For now, there is no scientific study that recommends a fourth jab. Even our virologists and epidemiologists have not insisted on taking it for now.” He, however, added that a study is being taken up at SJICSR to know the effectiveness of booster dose (third jab) and the report is awaited.

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Dr M K Sudarshan, chairman of the Covid-19 Technical Advisory Committee (TAC) said that in countries like Europe and the US, people are taking the fourth shot. “The vaccines in these countries are majorly Messenger RNA (mRNA)-based. These differ from the vaccines used in India like Covishield, Covaxin and the heterologous Corbevax. We do not have any data on the need for the fourth jab based on the Indian vaccines”. Measurable antibodies wane away six months after the vaccination.

However, the memory cells will be circulating for a lifetime and in the case of infection they will secrete antibodies. Keeping the immunogenicity of Indian vaccines, the protection capability and the current risk factors involved with no spike in cases and no major hospitalisation, there is no need for a fourth dose, he added.  

However, addressing the apprehension of healthcare and frontline workers who are exposed to the virus, the Union Health Ministry has sought data from AIIMS on the need for the fourth shot, Dr Sudarshan added. “For now, the focus is on improving the coverage of booster doses which is around 21 per cent. All those who have not taken the booster shots should immediately take it,” he advised.

Despite Covid testing incre­asing in Karna­taka at both the state and city level, the number of positive cases is not rising in proportion, TAC chairman Dr MK Sudarshan said. The TAC Committee has said that so far, the Covid-19 situation seems to be in control and is not expected to spiral. The number of tes­ts was increased from 1,500 to 5,000 at the city level, and from 5,000 to 15,000 at the state level. On the cont­rary, new and total active cases in the state have also seen a downhill trend.  He added that despite people not following Covid approp­riate behaviour (CAB), the scenario seems to be under control. The numbers have not risen exponentially in lieu of both international passengers and locals. At the previous TAC meeting, experts had estimated that the new variants will not cause a spike in the number of cases.

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