This is a summary, written by members of the CITF Secretariat, of:

Tauzin A, Benlarbi M, Medjahed H, Grégoire Y, Perreault J, Gendron-Lepage G, Gokool L, Morrisseau C, Arlotto P, Tremblay C, Kaufmann DE, Martel-Laferrière V, Levade I, Côté M, De Serres G, Bazin R, Finzi A. Humoral Responses against BQ.1.1 Elicited after Breakthrough Infection and SARS-CoV-2 mRNA Vaccination. Vaccines. 2023; 11(2):242.

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A partially CITF-funded, study, published in Vaccines, demonstrated that hybrid immunity, generated by vaccination and recent infection, induces higher humoral responses than vaccination alone against ancestral and Omicron variant BA.5 subvariant BQ.1.1 SARS-CoV-2 strains, regardless of which mRNA vaccine is administered. This study is a collaboration between Drs. Gaston de Serres (Institut National de Santé Publique du Quebec), Renée Bazin (Héma-Québec) and Andrés Finzi (Université de Montréal).

Key Findings:

  • Four weeks after the fourth dose of an mRNA vaccine in individuals with recent breakthrough infections, antibodies were able to recognize the ancestral spike glycoprotein better than those with no recent breakthrough infection, regardless of the mRNA vaccine type received.
  • Similarly, with respect to the spike glycoprotein of the BQ.1.1 subvariant, four months after dose three, individuals with a recent breakthrough infection exhibited better immune recognition of the spike antigen than those with no recent infection. Moreover, this difference in recognition remained more significant four weeks after the fourth dose.
  • Four weeks after the fourth dose, those with a recent breakthrough infection had a significantly higher level of neutralizing activity against the ancestral and the BQ.1.1 spike glycoprotein. All donors with recent breakthrough infection who received a fourth dose developed neutralizing antibodies against the BQ.1.1 spike, while some who received four doses of vaccine, but had no breakthrough infection, were still not able to neutralize the spike from this variant.
  • The Moderna BA.1 bivalent vaccine tended to induce better recognition and neutralization of the virus than the other vaccine platforms, including the Pfizer BA.4/5 bivalent vaccine. But these differences did not reach statistical significance; whether this is due to the relatively low number of samples tested remains to be determined.

The study included 63 individuals (25 males and 38 females; age range: 24-84 years). Of these, 20 individuals had a recent breakthrough infection with an Omicron sublineage (9 males and 11 females; age range: 24-67 years), between four weeks post-vaccine dose three and four months post-vaccine dose three, or between four months post-vaccine dose three and four weeks post-vaccine dose four. For the other donors (16 males and 27 females; age range: 31-84 years), no significant increase of the infection-acquired antibody levels was observed, although some of them had a history of infection.

Overall, the study supports that hybrid immunity led to better humoral and neutralization responses against the BQ.1.1 and other recent variants than vaccination alone.