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

Lapointe HR, Mwimanzi F, Cheung PK, Sang Y, Yaseen F, Kalikawe R, Datwani S, Waterworth R, Umviligihozo G, Ennis S, Young L, Dong W, Kirkby D, Burns L, Leung V, Holmes D, DeMarco DL, Simons J, Matic N, Montaner JSG, Brumme CJ, Prystajecky N, Niikura M, Lowe CF, Romney MG, Brockman MA, Brumme ZL. Serial infection with SARS-CoV-2 Omicron BA.1 and BA.2 following three-dose COVID-19 vaccination. Front. Immunol. 2022 September 6. Doi: 10.3389/fimmu.2022.947021.

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

A recent case report, now published in Frontiers in Immunology, indicates that Omicron reinfections – that is, two distinct infections with the Omicron variant at least 90 days apart – are possible, even in fully vaccinated individuals with an average immune response. The report is prepared by Drs. Mark Brockman and Zabrina Brumme (Simon Fraser University) and Dr. Marc Romney (University of British Columbia).

Key findings:

  • A healthcare worker, triply vaccinated with Pfizer-BioNTech’s Comirnaty mRNA vaccine, was diagnosed with an Omicron sub-lineage BA.1 infection in January 2022, 10 weeks after their third dose. Thirteen weeks later, the same individual experienced another Omicron infection, this time caused by the sub-lineage BA.2 variant. In both instances, the individual experienced moderate symptoms.
  • Before the first Omicron infection, the individual’s vaccine-induced antibody response was comparable to a group of similarly vaccinated individuals. Indeed, following the third dose, the individual’s concentration of receptor-binding domain (RBD) antibodies and their ability to neutralize both the original and Omicron BA.1 strains had increased compared to after the second dose.
  • The Omicron BA.1 infection boosted the individual’s vaccine-induced immune response against both sub-lineages (BA.1 and BA.2), despite not preventing a reinfection.

In conclusion, these results indicate that symptomatic Omicron reinfections in triply vaccinated individuals are possible, and that the additional immunity conferred by Omicron may not necessarily protect against Omicron re-infection.  Though vaccination was effective in its primary goal of preventing severe illness in this case, results highlight the importance of maintaining additional preventive measures to reduce transmission including mask wearing, and keeping up to date with  booster immunizations, as vaccine-induced immune responses naturally decline over time.

This article is a case report, meaning it is a detailed investigation of a noteworthy occurrence in a single individual. The analysis of this person’s immune response, however, is based on comparison with 124 other vaccinated individuals over the same time period.