Vaccines given to previously-infected individuals confer higher antibody counts enough to withstand new COVID variants, including Delta and Omicron, according to new study.

A Swiss research team found that the combined infection/vaccination immunity after breakthrough infections, could ultimately lead to broad immunity also against different (“non-homologous”) variants.

The new research, done by a team based in Switzerland, shows better protection is conferred by “hybrid immunity” — antibodies generated by prior infection and subsequent vaccination against SARS-CoV-2.

The study, posted on Friday (December 31, 2021), on the medRxiv bio server by a team led by Meriem Bekliz of the University of Geneva, shows that immunity from prior infection (or “infection-derived immunity”), independent of the infecting variant — is most likely “only poorly protective” against Omicron.

The study showed that blood samples from individuals who had been previously infected (known as “convalescent samples”) by pre-variant of concern (VOC) SARS-CoV-2 — such as Alpha, Beta, Gamma and Delta — “all showed a significant loss of neutralisation for Omicron.”

The magnitude of the loss of neutralisation ranged from 23-fold to 56.1-fold. It has not been peer-reviewed.

The researchers noted a 23.0-fold loss in Beta-convalescent, and up to 56.1-fold in Alpha-convalescent samples.

They also found that the Zeta variant showed a pronounced “escape” from neutralisation of up to 28.2-fold in Alpha convalescent samples.

This suggests that individuals with infection-derived immunity (from previous infection), regardless of the infecting variant, would benefit from vaccinations as a “booster shot”.

“In contrast to convalescent specimens, escape from neutralisation for Zeta was largely restored in vaccinated individuals, while Omicron showed a strongly reduced neutralisation of 85.7-fold compared to pre-VOC SARS-CoV-2m, the researchers claimed.

This bolsters the hypothesis that vaccinations help boost antibody generation of previously infected.

“Two-dose vaccinated individuals showed robust neutralization against B.1 and only slightly lower neutralization titers for Alpha, Beta, Gamma, Delta and Zeta, with fold-change reduction for heterologous virus between 2.8 (for Alpha) to 6.9 (for Beta),” the research stated.

“Robust neutralisation titers were observed in double-vaccinated individuals with subsequent Delta break-through infections, that also neutralised Omicron with a loss of only 12.5-fold,” the researchers pointed out.

Moreover, individuals with an Omicron breakthrough infection showed high neutralisation titers for both Delta and Omicron, with only a 1.5-fold loss for Delta neutralisation.

“This suggests that infection with antigenically different variants can boost immunity against variants that are antigenically similar to the vaccine strain.”

The researchers raised possibly important point as the pandemic progresses: “Geographic variation in the proportion of individual with infection- or vaccination-derived immunity or a combination of both could have substantial influence on the course of the pandemic.”

The study is preliminary. They noted that to fully assess the escape from neutralisation by new VOCs such as Omicron, the complexity of background immunity due to individual and regional differences needs to be taken into account.

The study bolsters previous research done in other countries that show higher antibody titres from vaccinations lead to less severity in previously-infected individuals. But it also highlights the necessity of the world to rally all resources available to vaccinate the “Global South”, especially African countries whose vaccination levels remain low.