A dose of science in the vaccination strategy

Vaccination and booster dose plans must have context in the backdrop and be informed by epidemiological evidence

February 08, 2022 12:02 am | Updated 12:02 am IST

Hand in blue medical gloves holding a vaccine vial with Covid 19 Vaccine Booster text, for Coronavirus booster shot.

Hand in blue medical gloves holding a vaccine vial with Covid 19 Vaccine Booster text, for Coronavirus booster shot.

Six weeks after the Indian government announced ‘precaution shots’ or the ‘third dose’ of COVID-19 vaccines for select populations, there have been four relevant developments. First, two COVID-19 vaccines have received ‘conditional market authorization’. Second, phase three clinical trials which include the booster dose of a nasal COVID-19 candidate vaccine have been approved. Third, the Omicron wave has largely swept through the country. Fourth, ₹5,000 crore has been allocated for COVID-19 vaccines in the Union Budget 2022-23.

What do these new developments mean for the COVID-19 vaccination and booster dose strategy in India? Do healthy adults need a booster and when? Is the budgetary allocation for COVID-19 vaccines enough? Let us discuss these.

Market authorisation

The news of market authorisation of Covishield and Covaxin has generated a lot of interest. Many have thought that from now on, anyone who wishes to, can buy a COVID-19 vaccine and have it administered at their will or on a doctor’s prescription. That is what ‘market authorisation’ usually means for most medical products. However, these two COVID-19 vaccines have received not the full but a ‘conditional’ market authorisation. Therefore, for the general public, nothing has changed. The Government will continue to regulate vaccine administration as earlier. The already eligible target groups (as per national guidelines), would continue to receive vaccines through authorised COVID-19 vaccination centres. The only effective change is for the vaccine manufacturers.

From submitting safety and efficacy data to the national drug regulator every fortnight, they can now submit this data every six months.

The nasal vaccine

Even though in the clinical trial stage, and none been authorised yet, nasal COVID-19 vaccines have always garnered a lot of interest for a variety of reasons. One, the ease of administration without a needle and syringe (and thus less biomedical waste). Two, given that COVID-19 vaccines currently in use in India have limited evidence about their role in reducing transmission, nasal vaccines, through mucosal antibodies, are likely to perform better in reducing transmission. Three, nasal vaccines might be useful for children, in whom the primary objective of COVID-19 vaccination is in reducing transmission rather than the individual benefit. Four, the world needs more vaccines to ensure wider availability and address vaccine inequity. Five, combination use of injectable and nasal vaccines might provide blended protection from severe disease and reduce the transmission. Such an approach could be useful in mitigating the impact of the ongoing COVID-19 pandemic as well as in the control of outbreaks in the post-pandemic period. However, a flip side of nasal vaccines and mucosal immunity is that protection is usually short lasting.

Epidemiological data and modelling estimates suggest that by the time the Omicron wave ends in any setting, 50% to 70% of the population could have been exposed. A study from South Africa found that the Omicron exposure in an individual with past infection or vaccination results in a 14-fold increase in antibodies, which offers protection from future Delta variant infection. The role of hybrid immunity acquired after natural infection in combination with two shots of COVID-19 vaccines provides better protection than vaccines alone. As an Omicron wave is sweeping through India, the country is at a stage which can be termed ‘sandwich immunity’ — hybrid immunity supplemented by another layer of natural infection.

In this backdrop, there is no reason for any urgency to administer COVID-19 booster doses to healthy adults in the age group 18 years-60 years. Similarly, children being at low risk of severe disease and having developed infections, and with further exposure of children in the ongoing Omicron surge, the vaccination of children younger than 15 years is also not an urgency, either.

This does not mean that no population sub-group in the 18-59 years band would ever need COVID-19 vaccine boosters. One, immunity, and thus protection against respiratory viruses (i.e., SARS-CoV-2), whether after vaccination or natural infection, declines over a period of time. Two, mutations are common in SARS-CoV-2 and the emergence of newer variants of concern with an ability to bypass immunity (provided by natural infection or vaccination) continues to remain a possibility. Therefore, it is likely that a larger proportion of the adult population might need a booster, though at a relatively longer interval. Furthermore, once there is evidence about the effectiveness of additional doses of COVID-19 vaccines (being used in India) in immunocompromised individuals, the third dose should be recommended for such adults, of any age group.

Funding of COVID-19 vaccines is a key operational issue. Soon after the Union Budget 2022-23, there were concerns that the allocation of ₹5,000 crore for COVID-19 vaccines could be insufficient. However, an objective assessment suggests that it could be enough. The Indian government, last year, had reportedly made an advance market commitment (AMC) with the manufacturers of Corbevax (Biological E Ltd.) for 30 crore shots and had made part-payment of ₹1,500 crore in advance. Therefore, the advance payment would be enough for 10 crore doses. The budgetary allocation for the next financial year could be sufficient to procure 20 crore to 33 crore doses, depending on the share of different COVID-19 vaccines ordered. In addition, there is likely to be a balance of stocks of COVID-19 vaccines already purchased in the current financial year. These doses are likely to be sufficient to vaccinate the remaining eligible population and administer boosters to (currently and in future) eligible population sub-groups.

Use the time at hand

In a pandemic response, efforts are made to reduce and halt any transmission. However, a fresh wave has a silver lining as well. Any natural infection results in the development of immunity. Therefore, the ongoing third wave gives India some time to decide about rolling out boosters for additional population sub-groups. This time at hand should be used for some reflection and actions. First, in the pandemic, epidemics, outbreaks and in epidemiology, context or the local situation matters a lot. The context of India is very different from that in other countries because of the relatively low median population age, the use of different COVID-19 vaccines, and the vaccination of the majority of the population after natural infection in the second wave, to list a few. Therefore, the data used by the other countries in deciding on vaccine effectiveness and boosters cannot, and should not, be used for India. Such decisions need to be based on the local data and evidence. For example, Denmark, after analysing local evidence, decided not to administer COVID-19 vaccines to children in the 5 years-12 years age group. A few vaccines administered to children in India, i.e., BCG against tuberculosis or Japanese encephalitis (JE) vaccines are not part of immunisation programmes of many countries. These are some of the examples of the context and use of local data.

Second, the success of any vaccination programme is dependent on citizen participation. It is time science determines the COVID-19 vaccination strategy. Let us, as citizens, not demand a booster for any adult age group. Let us not rush into the vaccination of children younger than 15 years of age. Let us not link vaccination to school attendance. Children need not to be vaccinated to attend school. The unscientific and misinformed public discourse has been an ongoing challenge in India’s COVID-19 pandemic response. Therefore, governments at all levels need to step up transparent and timely science communication around vaccines and through trustworthy sources.

Third, there is a need to identify vaccine and vaccination-specific policy questions. Thereafter, analyse the COVID-19 disease and vaccine data and link them with clinical outcomes to assess the effectiveness against SARS-CoV-2 variants and answer as many policy questions as possible. This needs to be supplemented by conducting primary research, both clinical and epidemiological, for the policy questions that have not been answered by the available data.

India’s COVID-19 vaccination drive has matured with commendable coverage: approximately 95% of eligible adults with one shot and 75% of eligible adults with both shots. However, the task is still unfinished. The sufficient COVID-19 vaccine supply or high vaccine coverage in adults is not reason enough to open booster doses for additional age groups. The COVID-19 vaccination and booster doses strategy should be determined by keeping context in the backdrop and being solely informed by emerging scientific and epidemiological evidence. Alongside, rather than being solely focused on COVID-19 vaccines and boosters — in the weeks and months — we, as a society, need to come to a consensus and prepare a road map to ‘live with SARS-CoV-2’.

Dr. Chandrakant Lahariya, a physician-epidemiologist, is affiliated with the Foundation for People-centric Health Systems, based in New Delhi

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