Covid-19: Booster shots nice to have, but not SA priority

Booster shots may offer over-60s an almost 20-fold increase in protection against severe Covid-19, research on fully vaccinated people in Israel shows.

But scientists noted in the journal Nature that the findings "do not indicate a 'strong need' for boosters" given the study's limitations.

In SA, ramping up the number of people getting their first shot is a priority and booster shots are not, say top clinicians.

Dr Jeremy Nel, an infectious diseases specialist at Wits University, said: "Any benefits from boosting immunity to the current viral strains would mostly be to prevent the milder forms of the disease, since all the vaccines are already good at preventing severe disease.

"The key goal should be to vaccinate as many high-risk people as possible once, since that's what will prevent the vast majority of severe disease and death."

High coverage of over-35s is the priority, said Wits University vaccinologist professor Shabir Madhi. "This will be most impactful in ensuring we don't have overwhelming of health services when we experience another resurgence, and that the number of deaths are few," he said.

The Israeli observational study evaluated data from 1.1-million over-60s who had a third jab of the Pfizer-BioNTech vaccine more than five months after their first two doses.

Twelve days later, this group were 19.5 times less likely to get severe Covid-19 compared to their peers who had received a double dose, and 11.3 times less likely to be infected with the virus.

This might be the "most robust data" yet in favour of boosters, University of Pennsylvania biostatistician Susan Ellenberg told Nature.

But Boston University epidemiologist Ellen Murray cautioned in the report that the potential biases of observational studies and "insufficient evidence for waning immunity after vaccination" don't justify boosters.

Two reviewers found the "short-term effect [of boosters] would not necessarily imply worthwhile long-term benefit".

Monitoring the frequency and severity of breakthrough infections and the age and co-morbidities of infected individuals would inform decisions about possible targeted boosters, said professor Graeme Meintjes, an infectious diseases expert at the University of Cape Town.

Some groups are likely to require booster doses every two to three years, based on a modelling exercise, Madhi noted, and Nel said boosters could eventually be useful for three reasons.

"Firstly, some groups of people might not get the maximum amount of protection from a standard vaccination course. For example, people on chemotherapy, or immunosuppressive drugs.

"The second reason would be if immunity wanes significantly with time. This is currently a matter of a lot of debate .

"The third reason would be if it's possible to boost everyone's immunity a bit, even if it doesn't wane, to help prevent especially the milder forms of the disease."

A number of high-income countries are considering booster vaccines or, like Israel, have already implemented them.

Low-income countries are still struggling to secure access to vaccines, according to the World Health Organisation, which has appealed for a pause on booster shots until coverage is higher worldwide.

High-income countries have given 48 times more jabs per person than low-income nations, according to the global health body.

Wits professor of medicine Francois Venter said South Africans do not need booster shots yet. "The current Pfizer and J&J work brilliantly. We can afford to wait and see what data emerges on this. We will know soon."