Rethink the booster shot strategy

The choice of age group, vaccine and eligibility duration for booster shots appears problematic

India’s booster programme, in comparison, started on January 10, 2022, covering 4.3 million within a week. India has a lot of catching up to do with respect to both primary (two-dose) and secondary (booster) vaccination.
India’s booster programme, in comparison, started on January 10, 2022, covering 4.3 million within a week. India has a lot of catching up to do with respect to both primary (two-dose) and secondary (booster) vaccination.

By Ali Mehdi 

Within a year of its Covid-19 vaccination drive, India has managed to administer the second-highest number of Covid-19 vaccine doses in the world—1.57 billion vis-à-vis China’s 2.94 billion. China had also managed to administer booster doses to 331 million of its population by January 6, 2022. India’s booster programme, in comparison, started on January 10, 2022, covering 4.3 million within a week. India has a lot of catching up to do with respect to both primary (two-dose) and secondary (booster) vaccination.

At the moment, ‘precautionary’/booster shots are being administered to health care workers, front line workers and >60 year olds with co-morbidities, who completed their full vaccination 39 weeks ago. The booster shot will be of the same vaccine as the first and second doses. The choice of age group, vaccine and eligibility duration for precautionary shots appears problematic.

As far as trget age-group is concerned, the prevalence of co-morbidities of concern (CoC), from the perspective of Covid-19, is extremely high—actually, much higher—in the under-60 age groups in India, as per the Global Burden of Diseases (GBD) 2019. According to th e US Centers for Disease Control and Prevention (CDC), people of any age with CoCs are more vulnerable to severe illness from Covid-19. Most diseases listed in GBD also appear in the CDC’s and the Indian health ministry’s lists of CoCs (bit.ly/3tuZVKd).

Secondly, while booster shots are needed, fully vaccinating the unvaccinated/partially vaccinated should be our top priority. With the prevalence level of CoCs, we need to be particularly focused on the 30% of our adult population that is still not fully vaccinated. With India being the world’s largest contributor to premature deaths (under 70 years) over the past three decades, the adult unvaccinated/partially vaccinated with CoCs remain at great risk of severe disease and death in particular. The same strategy should be adopted vis-à-vis booster shots—with priority assigned based on risk of severe disease, hospitalisation and death due to Covid-19, rather than age and occupation. The three groups identified at the moment for booster doses are definitely at great risk, but at the same time, there are many outside these groups at similar or greater risk.

Researchers from India’s National Centre for Disease Control found that Covid-19 mortality in India’s working-age population, especially 45-59 year olds, was significant. Accordingly, they argued that ‘it is imperative for the government to prioritise this age group in their targeted interventions’ (bit.ly/3GB7N0p). Another study of Covid-19 deaths in India, involving several researchers from AIIMS New Delhi, including its director, Dr Randeep Guleria, found that 42% of the deceased were in the age-group of 18-50 years, 35% in 51-65 years and 23% in 65+ years (bit.ly/326uJ8F). Since the working-age population is more externally active, its exposure to Covid-19, and deaths due to it, is also understandably higher. This segment of the population with co-morbidities also needs to be included in the booster drive, from the perspective of lives as well as livelihoods. The risk of severe disease, hospitalisation and death should be the only criterion for the booster shot programme. However, the first priority should be to fully vaccinate those at such risk.

As far as the choice of booster vaccine is concerned, while the health ministry claims that India’s Covid-19 vaccination program is based on ‘scientific and epidemiological evidence, as per ‘WHO guidelines and global best practices’, this does not appear to be the case. A recent interim-statement from WHO holds, given ‘evolution of the virus, a vaccination strategy based on repeated booster doses of the original vaccine composition is unlikely to be appropriate or sustainable’. While this is a general statement regarding the limitation of existing Covid-19 vaccines—with WHO recommending that the composition of these vaccines needs to be updated to deal with virus evolution, until we have vaccines ‘that have high impact on prevention of infection and transmission, in addition to the prevention of severe disease and death’—other international health agencies of repute such as the CDC and the European Medicines Agency (EMA) have allowed heterologous (‘mix and match’) boosters. In a recent report, the EMA argued that ‘in general heterologous boosting is immunogenic…with no specific safety concerns emerging to date.

Especially when boosting with a mRNA vaccine, immune responses, estimated as binding and/or neutralising antibodies, are similar or higher than homologous mRNA boosting and higher than homologous vector boosting including against variants of concerns’ (bit.ly/3rnl2vm). In a recent statement, the WHO supported ‘a flexible approach to homologous versus heterologous vaccination schedules’, even considering ‘two heterologous doses of any EUL COVID-19 vaccine to be a complete primary series’. India should allow heterologous primary vaccination as well.

Finally, it should also consider reducing the duration after full vaccination for the booster shot—the CDC, for instance, allows it after two months of primary vaccination with Johnson & Johnson’s vaccine or five months after Pfizer-BioNTech’s and Moderna’s. Since the booster shot is expected to maintain or enhance immunity after primary vaccination, its timing should ideally be different for different people, depending on their level of immunity, rather than a fixed term for everyone.

The author is Senior visiting fellow at ICRIER Views are personal

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