How good is it to develop new vaccines that protect against serious diseases?

If the increase in new variants continues to outpace new boosters, is there any benefit to updating vaccines at all?

Cromer said: “We want to balance the cost of updating a new vaccine with the money we have to pay the vaccine manufacturer and the potential profit we can get from it.”

Enhanced protection

To pinpoint that advantage, Cromer and colleagues used studies that compared the neutralizing titers produced by different vaccines, or the levels of vaccine-destroying antibodies in people's blood.

“Even after accounting for all the obvious differences between the groups, neutralizing antibody titers essentially increased by 40 percent with each update of the vaccine,” Cromer says.

This amounts to a 40% increase in antibody response with each new vaccine. And that improvement applies not only to the specific variant that people have been vaccinated against, but also to the various new coronavirus strains that we are exposed to.

However, a 40% increase in neutralizing titer does not automatically result in a 40% increase in protection against symptomatic and severe disease.

Previously data analysisCromer and colleagues established a quantitative relationship between the level of neutralizing antibodies in the blood and protection from the new coronavirus.

They used this relationship to predict the impact that a 40% increase in antibodies would have on clinical outcomes.

They estimate that the newer boosters offer 11 to 25 percent more protection against symptomatic disease and 23 to 33 percent more protection against severe disease compared to older boosters.

How do the numbers stack up?

So how impressive is the increase in booster output? It depends which way you look at it.

“There are definitely benefits to continually updating vaccines, but it wasn't necessarily what I expected,” Cromer said.

“But I also think that the benefit is relatively small, perhaps smaller than some people were expecting. We don't typically authorize vaccines based on 20-30% efficacy. So these The speed with which new vaccines are put into use must be balanced against their potential costs.”

For Associate Professor Paul Griffin, an infectious disease expert at the University of Queensland who was not involved in the study, the findings highlight the benefits of a faster vaccine rollout.

“40% is a useful improvement,” Griffin said. “But the improvement could have been even greater had there not been delays in the rollout of these vaccines.”

He said faster regulatory processes, Australia's ability to manufacture RNA vaccines and better designed vaccines containing multiple variants would improve the ability to protect people with future boosters.

Professor Catherine Bennett, head of epidemiology at Deakin University, said the study's 40 per cent results had wide confidence intervals, or statistical guardrails around the final estimate. Researchers say their best guess is 40%, but the actual improvement between each vaccine could be as low as 7% or as high as 82%.

“It could be a stronger effect, or it could be a weaker effect. This study doesn't have the precision to show that,” she says. “But what this study shows is that with more recent vaccines, you get a better neutralizing response.”

The pattern of enhanced vaccine efficacy is welcome, but given the discrepancies between vaccines and variants, we don't know exactly why there is any certainty of enhanced efficacy. And that pattern may not last forever.

In any case, Cromer says if you're in a vulnerable population and are planning to get a booster shot, you don't need to wait for a prescription for the new vaccine. People who have recently received a booster shot are less likely to develop severe symptoms, be hospitalized, infect others, or be infected with the coronavirus for a long time.

“Getting vaccinated is much more important than getting vaccinated against the latest variants.”