Dans une récente étude publiée sur medRxiv* serveur de préimpression, les chercheurs ont estimé l’efficacité des vaccins monovalents contre la maladie à coronavirus de l’acide ribonucléique messager (ARNm) 2019 (COVID-19) contre le syndrome respiratoire aigu sévère coronavirus 2 (SARS-CoV-2) Variante Omicron préoccupante (COV) résultats de gravité de l’infection parmi adultes.
L’émergence continue de nouveaux sous-COV d’Omicron a menacé l’efficacité des vaccinations primaires et des agents thérapeutiques tels que les anticorps monoclonaux, justifiant des vaccinations de rappel (troisième dose). L’évaluation de l’efficacité des vaccinations de rappel de l’ARNm COVID-19 pourrait éclairer la planification de l’administration des doses de rappel afin de réduire le fardeau sanitaire mondial du COVID-19.
À propos de l’étude
Dans la présente étude test-négative (TN), les chercheurs ont évalué l’efficacité du vaccin monovalent à ARNm COVID-19 (VE) par rapport aux résultats de gravité des infections à Omicron.
L’étude comprenait des résidents de la communauté âgés de 50 ans et plus avec ≥ 1 rapport RT-PCR (réaction en chaîne par polymérase de transcription inverse) pour le SRAS-CoV-2 entre le 2 janvier 2022 et le 1er octobre 2022. Les participants ont été stratifiés en fonction du temps écoulé depuis COVID-19 vaccination et âge. Omicron a été détecté dans presque tous les échantillons positifs pour le SRAS-CoV-2 fin janvier 2022. L’équipe a exclu les personnes hospitalisées dont les échantillons ont été obtenus> 3,0 jours après l’hospitalisation et celles atteintes d’infections nosocomiales.
Le résultat de l’étude était l’hospitalisation ou les décès associés au COVID-19. Estimations VE [two-dose (D2), three-dose (D3), and four-dose (D4) doses in comparison to non-vaccinated individuals) and marginal VE estimates (D3 or D4 vs. D2) against Omicron infection-associated hospital admissions and deaths were evaluated. In addition, VE during the predominance of Omicron BA.1/BA.2 (between 2 January 2022 and 2 July 2022) and BA.4/5 (between 3 July and 1 October 2022) sub-VOCs were compared.
Delta infections were detected based on WGS (whole genome sequencing) analysis or positive reports for the SARS-CoV-2 spike (S) gene in the target positive screening obtained before 24 January 2022 (n=72). Multivariable logistic regression modeling was used for the analysis. The TN design was applied to SARS-CoV-2 testing at laboratories of Canadian provinces, health administrative datasets, and COVID-19 vaccinations.
Results
The mean values for the age of cases and controls were 77 years and 66 years, respectively, and 57% of cases and 37% of controls were men. Among the study groups, the proportions of non-vaccinated individuals among cases and controls were 28% and five percent, respectively. Compared to the non-vaccinated, more COVID-19 vaccinees were women, had been administered influenza vaccinations, and resided in moderate- or high-income areas.
Among the vaccinees, more D2 vs. D3 or D4 were from low-income areas, and fewer had received influenza vaccinations. The sub-VOCs distributions were 50% and 50% for BA.1 and BA2, respectively, during BA.1 and BA.2 predominance and 10% and 90% for BA.4 and BA.5, respectively, during BA.4/BA.5 predominance.
A total of 11,160 and 62,880 individuals with Omicron infection-associated severity outcomes and TN symptomatic control individuals, respectively, were considered for the analysis. Compared to non-vaccinated individuals, the VE estimates ranged between 91% and 98% seven days to 59 days post-D3 but reduced to 76% to 87% after ≥8.0 months.
Seven to 59 days post-D4, VE restored between 92% and 97% but reduced to 86% to 89% after ≥4.0 months. Consistent trends in marginal VE were observed. The VE estimates were lower during Omicron BA.4/5 predominance compared to those observed during Omicron BA.1 and BA.2 predominance based on a similar number of days elapsed since COVID-19 vaccination. Differences in the VE estimates may have been observed due to greater immune-evasiveness of Omicron BA.4 and Omicron BA.5.
Conclusions
Overall, the study findings showed that D3 or D4 boosters of mRNA SARS-CoV-2 vaccinations of the monovalent type initially reinstituted robust immunity against hospitalizations and deaths associated with Omicron infections among all community-residing (especially elder) individuals. However, VE reduced with time, indicative of immunity waning, especially during the BA.4/5-dominant period.
Even though the vaccination-induced immune protection persisted at high levels four months D4 irrespective of age, whether the waning of immunity increases beyond four months is uncertain. The finding, in conjunction with the lower VE estimates against Omicron BA.4/5 and the probability of even lower efficacy against the novel XXB and BQ.1.1 strains, underpins booster administrations.
In addition, non-pharmaceutical interventions (NPIs) such as face mask use, social distancing, improved ventilation, and indoor air filtration could aid in mitigating the impact of existing Omicron sub-VOCs and those that are yet to emerge. Given the paucity of data against Omicron BA.4/5, novel strains, and bivalent vaccine introduction, continued VE monitoring efforts are required. Further research must be conducted to evaluate VE estimates for all Omicron sub-VOCs individually and must incorporate rapid antigen test results.
*Important notice
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
