Association between the COVID-19 pandemic and pertussis in France using multiple nationwide data sources

Abstract

Background: Interventions to mitigate coronavirus disease 19 (COVID-19) pandemic may impact other respiratory diseases such as pertussis. We aimed to study the course of pertussis in France over an 8-year period and its association with COVID-19 mitigation strategies, using multiple nationwide data sources. Methods: We analyzed the number of French pertussis cases between 2013 and 2020, using the PCR test results from nationwide outpatient laboratories (Source 1) and the pediatric network of 41 hospitals (Source 2), and using the reports of an office-based pediatric national network (Source 3). We conducted a quasi-experimental interrupted time-series analysis, relying on negative binomial regression models. The models accounted for seasonality, longterm cycles, and secular trend, and included a binary variable for the first national lockdown (ordered on March 16, 2021). Results: We identified 19,039 cases of pertussis from the three data sources during the study period. There was a significant decrease of pertussis cases following the implementation of mitigation measures, with adjusted incidence rate ratios of 0.102 (95% CI 0.040-0.256) and 0.216 (95% CI 0.071-0.656) for Source 1 and Source 2, respectively. The association was confirmed in Source 3 (median of 1 [IQR 0-2] vs. 0 [IQR 0-0] pertussis cases per month before and after lockdown, respectively, p=0.0048). Conclusion: The drastic reduction of outpatient and hospitalized cases of pertussis strongly suggests an impact of COVID-19 mitigation measures and their consequences on pertussis epidemiology. Pertussis vaccination recommendations should be carefully followed, and disease monitoring should be continued to detect any resurgence after relaxation of mitigation measures.

Pertussis surveillance results from a French general practitioner network, France, 2017 to 2020

“…However, in another study published in 2021, the number of positive B. pertussis PCR tests obtained by two French laboratories (which carry out more than 90% of the testing for pertussis outside hospitals, in mainland France) were described between 2013 and 2020. In 2017, 2018, 2019 and 2020, respectively 3,354, 3,233, 2,783 and 606 positive PCRs were found [21]. Even taking into account that our surveillance system also includes cases confirmed by culture, as well as epidemiologically-confirmed cases, and recognising the large CIs, the incidences we found (11,238; 95% CI: 7,681-14,795 in 2017; 6,276; 95% CI: 3,585-8,967 in 2018; 10,130; 95% CI: 6,956-13,304 in 2019; and 1,910; 95% CI: 732-3,088 in 2020) are higher than incidences suggested by these laboratory results.…”