Come 1 May, here’s why science says vaccination should not merely be linked to age cut-offs

Scientists from Jawaharlal Nehru Centre for Advanced Scientific Research say that amid current vaccine shortage, a priority system could help protect the most vulnerable first.

Representational image | People wait for their turn to get the first dose of the Covid-19 vaccine | ANI

Bengaluru: Scientists from Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, have developed a model, which suggests that optimising distribution of vaccines if a country is facing a shortage can end up saving more lives, now that vaccinations are set to open for all adults and the spread of the pandemic is not uniform across the country.

As India reels under a tsunami of new Covid cases and deaths, the need of the hour is to expedite vaccinations to protect millions that are part of the vulnerable population. However, with the country facing a vaccine shortage, this seems to be a more difficult task than earlier assumed.

To tackle this shortage, the JNCASR researchers recommend optimising vaccine distribution according to local strategy of availability and risk, rather than an indiscriminate rollout.

In a pre-print, authors Brijesh Saraswat, Santosh Ansumali and Meher K. Prakash, laid out the details of their model and projections based on various vaccination scenarios and concluded that vaccinating adults from multigenerational homes could save several lives.

“Strategically vaccinating the adults from multigenerational homes in India may be effective in saving the lives of around 70,000 to 200,000 of seniors, under the different epidemiological scenarios possible with or without strict lockdowns,” the study notes.

When the pandemic began, it was obvious that the risk of death increased with an increase in age and therefore, prioritising by age was reasonable when vaccines began to be rolled out.

However, at this stage where vaccines will now be administered to everyone above 18, a next phase of prioritisation strategy is required, say the authors.

They add that it should be based on three parameters locally: Vaccine availability, incidence of Covid and age demographics.

The authors argue that irrespective of whether seniors at home are vaccinated or not, all their contacts within their households should be.

Vaccination strategy benefits

“The fear with this disease is not with infections,” study author Meher Prakash told ThePrint. “The fear is with hospitalisation and death. We wouldn’t care if infections climbed ten times or hundred times if they were not affecting anyone seriously.”

And vaccines have shown to reduce this risk of severe and critical disease, even after just one shot.

“There is only a limited capacity of vaccines,” said Prakash, “And we have to vaccinate as many people as possible.”

However, the researchers noted that some senior citizens and other vulnerable people are likely to remain unvaccinated due to various reasons. This can prove to be harmful as according to hospital statistics, vaccinating seniors is more effective than the younger population.

Therefore, the authors propose that the younger family members of such senior citizens should be vaccinated to break the chain of transmission.

Using a formula, the authors calculated the “effective risk” of an adult in a household based on four factors — the infection fatality rate (the number of infected who die), transmission at home (secondary attack rate), chances of infecting a senior and mortality risk of a senior.

They then used this number to calculate the effective age of all individuals in a house, depending on how vulnerable members of the household are. If others in the house are vulnerable, each person’s effective age went up with risk.

The researchers stated that in a house with an unvaccinated senior citizen who is a parent, an adult gains 15 years more in effective age while with an unvaccinated grandparent, the gain is 40 years.

Prakash also pointed out that in households with at-risk family members who are unable to get vaccinated, such as those with HIV, the effective age of all adults increases as well.

Therefore, just like in the case with unvaccinated senior citizens, he proposes vaccinating everybody else at home to offer protection to the individual who cannot get inoculated.

When following such a strategy of vaccinating those with high effective risk and age, the number of transmissions from adults in the family is likely to be reduced by over 1,00,000, according to the authors, assuming the second wave lasts about three to six months.

Prioritising a strategy based on vaccinating multigenerational homes is not new and it is done for the flu, Prakash told ThePrint.

While this strategy works well in the long-term, it is crucial for the short term as well, the authors noted.

The next three months are critical with the current second wave, stressed Prakash. “We obsess over the peak of the wave and when it will come, but the projected peak can’t dictate our actions; our actions decide when the peak occurs,” he said.
​
​He added, “If we want to work backwards from three months in the future [where the wave has subsided], who do we target now?”

(Edited by Rachel John)