© The Indian Express Pvt Ltd
Tags:
Journalism of Courage
Given that the BF.7 variant that is dominant in China has greater immune escape potential and a shorter incubation period, the Indian government has made testing mandatory for travellers from certain countries.
BF.7 has previously been detected in India. Is it likely to cause a surge now?
Indeed. Not a worrisome one, though. BF.7 has the strongest infection ability of all Omicron sub-variants, including BA.1 and BA.2. Its R-number (rate of infectivity) is estimated to be higher than 10, possibly even R18.6. This, on the lower side of the estimate, translates into one case becoming a billion cases in nine steps. Besides, BF.7 has a higher immune escape capability and a shorter incubation period than all previous variants.
Unfortunately, the virus has so far always been a step ahead of us. So we cannot be certain of what it will do next and when. We should always be prepared for the worst case scenario while hoping for the best.
What is the most effective way of maintaining surveillance, given that most people are unlikely to get tested, or test using a home kit?
The WHO provides periodically revised guidelines on ideal surveillance of Covid-19. The purpose of surveillance is to identify changes in epidemiological patterns, trends, and to accordingly prepare the healthcare capacity. In its new revision, WHO has added the importance of genomic surveillance to identify sub-variants that are in circulation.
While it is indeed a challenging task, continuing testing and serosurveys in priority groups is the most effective method for planning policy. The Tata Institute for Genetics and Society (TIGS), Bengaluru, has been conducting environmental surveillance of Covid-19. It has been collecting wastewater samples from 28 sewage treatment plants in Bengaluru since August last year to monitor the real-time spread of Covid. Similar testing can be done elsewhere too.
Is there need to revert to work-from-home and mask mandates to prevent a surge?
Prevention is always a good strategy. Even though India is not seeing a substantial surge at the moment, maintaining social distancing, wearing masks, and respiratory and hand hygiene measures can go a long way in curtailing surges.
The Institute for Health Metrics and Evaluation estimated that cases are 133 per 100,000 people while reported cases are 0.74 per 100,000 people. So, there is a substantial gap between reported and estimated cases. Cases can be reduced by half if 80 per cent of the population reverts to wearing masks.
Are the current vaccines effective against BF.7?
Global vaccination campaigns have resulted in considerably improved control of SARS-CoV-2. However, a study in the New England Journal of Medicine on vaccine efficacy against the Omicron B.1.1.529 variant reported that ChAdOx1 nCoV-19 (Covishield) did not provide protection after 25 weeks of two doses; the efficacy, however, increased with booster shots.
A meta-analysis in The Lancet reported that one month after the primary vaccination (two doses), vaccine effectiveness against severe Covid-19 disease was lower for Omicron compared to other variants. Vaccine effectiveness against Omicron decreased rapidly from one to six months after the primary vaccine series.
Research on the BF.7 variant is still in the works. However, based on previous data, it can be estimated that the efficacy of current vaccines against the new variants has declined in varying degrees.
Is there a need for a fourth dose, especially for those at the front line?
Yes. The meta-analysis in The Lancet suggested that booster vaccination increased vaccine effectiveness against Omicron-induced severe disease. Immunity built by boosters remained high four months after vaccination.
Does India need a bivalent vaccine, like those that have been approved outside?
The new booster is a bivalent vaccine, which means it contains two messenger RNA (mRNA) components of the coronavirus. One half of the vaccine targets the original strain, and the other half targets the BA.4 and BA.5 Omicron sub-variant lineages, which were predicted to continue circulating this fall and winter.
In a preprint published in December 2022 on medRxiv, researchers evaluated the bivalent [encoding spike (S) proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) D614 strain and the Beta variant of concern (VOC)] vaccine efficacy (VE) against the Omicron VOC. India was among the countries the second stage of the study was conducted in.
The study found that the bivalent Covid-19 vaccine conferred heterologous immune protection against symptomatic Omicron BA.1 sub-VOC and Omicron BA.2 sub-VOC infections among adult individuals with prior SARS-CoV-2 exposure.
With so many people continuing to get the infection, could a more transmissible or virulent variant arise?
It is possible, though not probable. There have been four major variants of SARS-CoV-2, and over 50 mutations have been identified. The virus is rapidly changing and adapting to us. We cannot predict how many variants may emerge and how they may change. The trend so far suggests the virus is getting faster and stronger in its ability to infect. However, it is less severe in its lethality.
Vaccination and infection-induced immunity have a major role to play in this as well. We must always keep in mind that the Covid-19 pandemic is not over. We need to continue working at the individual and collective levels to emerge triumphant from this monumental disaster.
Dr Parikh is Hon. Director, Medical Research, Jaslok Hospital and Research Centre, and the author of two national bestsellers on Covid-19 and vaccination. He spoke with Kaunain Sheriff M.
