Effectiveness of BNT162b2 and CoronaVac vaccines against omicron in children aged 5 to 11 years

Real-world effectiveness of original BNT162b2 mRNA COVID-19 against symptomatic Omicron infection among children 5-11 years of age in Brazil: A prospective test-negative design study

OBJECTIVE

To estimate original wild-type BNT162b2 effectiveness against symptomatic Omicron infection among children 5-11 years of age.

METHODS

This prospective test-negative, case-control study was conducted in Toledo, southern Brazil, from June 2022 to July 2023. Patients were included if they were aged 5-11 years, sought care for acute respiratory symptoms in the public health system, and were tested for SARS-CoV-2 using reverse transcription polymerase chain reaction. In the primary analysis, we determined the effectiveness of two doses of original wild-type BNT162b2 against symptomatic COVID-19. The reference exposure group was the unvaccinated.

RESULTS

A total of 757 children were enrolled; of these, 461 (25 cases; 436 controls) were included in the primary analysis. Mean age was 7.4 years, 49.7 % were female, 34.6 % were obese, and 14.1 % had chronic pulmonary disease. Omicron accounted for 100 % of all identified SARS-CoV-2 variants with BA.5, BQ.1, and XBB.1 accounting for 35.7 %, 21.4 % and 21.4 %, respectively. The adjusted estimate of two-dose vaccine effectiveness against symptomatic Omicron was 3.1 % (95 % CI, -133.7 % to 61.8 %) after a median time between the second dose and the beginning of COVID-19 symptoms of 192.5 days (interquartile range, 99 to 242 days).

CONCLUSION

In this study with children 5-11 years of age, a two dose-schedule of original wild-type BNT162b2 was not associated with a significant protection against symptomatic Omicron infection after a median time between the second dose and the beginning of COVID-19 symptoms of 192 days, although the study may have been underpowered to detect a clinically important difference.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov number, NCT05403307 (https://classic.

CLINICALTRIALS

gov/ct2/show/NCT05403307).

Outcomes of SARS-CoV-2 and Seasonal Viruses Among Children Hospitalized in Brazil

BACKGROUND AND OBJECTIVES

Understanding how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) interacts with other respiratory viruses is crucial for developing effective public health strategies in the postpandemic era. This study aimed to compare the outcomes of SARS-CoV-2 and seasonal viruses in children and adolescents hospitalized with severe acute respiratory infection (SARI).

METHODS

This population-based, retrospective cohort study included children and adolescents hospitalized with SARI from February 2020 to February 2023 in Brazil. The main exposure of interest was viral etiology. The primary outcome was in-hospital mortality. Competing risk analysis was used to account for time dependency and competing events.

RESULTS

A total of 235 829 patients had available results of the viral tests, with SARS-CoV-2 predominance. According to the competing-risk survival analysis, the estimated probability of a fatal outcome at 30 days of hospitalization according to the viral strain was 6.5%, 3.4%, 2.9%, 2.3%, 2.1%, and 1.8%, for SARS-CoV-2, coinfection, adenovirus, influenza, other viruses, and respiratory syncytial virus, respectively. Individuals with a positive test for SARS-CoV-2 had hazard of death 3 times higher than subjects with a negative test (hazard ratio, 3.3; 95% confidence interval, 3.1-3.5). After adjustment by the competing-risk multivariable analysis, admission in Northeast and North regions, oxygen saturation <95%, and the presence of comorbidities were risk factors for death in all viral strains.

CONCLUSIONS

SARS-CoV-2 infection had the highest hazard of in-hospital mortality in this pediatric cohort hospitalized with SARI. Regardless of viral etiology, the presence of underlying medical conditions was a risk factor for death.

Associations between COVID-19 Vaccination Status and Self-Reported SARS-CoV-2 Infection among 8538 Children Aged 3-17 Years during a Massive COVID-19 Outbreak after China Changed Its Zero-COVID-19 Policy: A Cross-Sectional Survey

This study aimed to investigate the associations between COVID-19 vaccination status and self-reported SARS-CoV-2 infection among children and adolescents aged 3-17 years during a massive COVID-19 outbreak after China changed its zero COVID policy. A cross-sectional online survey was conducted between 1 and 9 March 2023. Participants were the parents of children studying in kindergartens, primary schools, or secondary schools in Shenzhen. Convenient sampling was used. All kindergartens, primary schools, and secondary schools in the Longhua District of Shenzhen invited the parents of children and adolescents attending the schools. Interested parents completed an online survey. Multivariate logistic regression was fitted. Among 8538 participants, 40.9% self-reported that their children had SARS-CoV-2 infection after 7 December 2022, where 92.9% of them received two doses of the COVID-19 vaccines, and 74.6% received their second dose for more than six months. In multivariate analysis, children who received their second dose of the COVID-19 vaccination for no more than three months had a lower SARS-CoV-2 infection rate compared to unvaccinated children (<1 month: AOR: 0.17, 95% CI: 0.07, 0.44; 1-3 months: AOR: 0.54, 95% CI: 0.41, 0.75). The duration of protection conferred by the primary COVID-19 vaccination series was relatively short among children. A booster dose should be considered for children.