Underdetection of cases of COVID-19 in France threatens epidemic control.

As countries in Europe gradually relaxed lockdown restrictions after the first wave, test-trace-isolate strategies became critical to maintain the incidence of coronavirus disease 2019 (COVID-19) at low levels1,2. Reviewing their shortcomings can provide elements to consider in light of the second wave that is currently underway in Europe. Here we estimate the rate of detection of symptomatic cases of COVID-19 in France after lockdown through the use of virological3 and participatory syndromic4 surveillance data coupled with mathematical transmission models calibrated to regional hospitalizations2. Our findings indicate that around 90,000 symptomatic infections, corresponding to 9 out 10 cases, were not ascertained by the surveillance system in the first 7 weeks after lockdown from 11 May to 28 June 2020, although the test positivity rate did not exceed the 5% recommendation of the World Health Organization (WHO)5. The median detection rate increased from 7% (95% confidence interval, 6-8%) to 38% (35-44%) over time, with large regional variations, owing to a strengthening of the system as well as a decrease in epidemic activity. According to participatory surveillance data, only 31% of individuals with COVID-19-like symptoms consulted a doctor in the study period. This suggests that large numbers of symptomatic cases of COVID-19 did not seek medical advice despite recommendations, as confirmed by serological studies6,7. Encouraging awareness and same-day healthcare-seeking behaviour of suspected cases of COVID-19 is critical to improve detection. However, the capacity of the system remained insufficient even at the low epidemic activity achieved after lockdown, and was predicted to deteriorate rapidly with increasing incidence of COVID-19 cases. Substantially more aggressive, targeted and efficient testing with easier access is required to act as a tool to control the COVID-19 pandemic. The testing strategy will be critical to enable partial lifting of the current restrictive measures in Europe and to avoid a third wave.

Using the near real-time effective reproduction number rt as an early-warning tool for seasonal bronchiolitis and influenza-like illness epidemics.

BACKGROUND: Yearly bronchiolitis and influenza-like illness epidemics in France often involve high morbidity and mortality, which severely impacts healthcare. Epidemics are declared by the French National Institute of Public Health based on syndromic surveillance of primary care and emergency departments (ED), using statistics-based alarms. Although the effective reproduction number (Rt) is used to monitor the dynamics of epidemics, it has never been used as an early warning tool for bronchiolitis or influenza-like illness epidemics in France.We assessed whether Rt is useful for detecting seasonal epidemics by comparing it to the tool currently used (MASS) by epidemiologists to declare epidemic phases. METHODS: We used anonymized ED syndromic data from the Île-de-France region in France from 2010 to 2022. We estimated Rt and compared the indication of accelerated transmission (Rt >1) to the MASS epidemic alarm time points. We computed the difference between those two time points, time to epidemic peak, and the daily cases documented at first indication and peak. RESULTS: Rt provided alarms for influenza-like illness and bronchiolitis epidemics that were, respectively, 6 days (IQR[4;8]) and 64 days (IQR[52;80]) - in median - earlier than the alarms provided by MASS. CONCLUSION: Rt detected earlier signals of bronchiolitis and influenza-like illness epidemics. Using this early-warning indicator in combination with others to declare an annual epidemic could provide opportunities to improve healthcare system readiness.

Factors associated with vaccine adherence among an underserved population: the adult Travellers in Nouvelle-Aquitaine, France.

BACKGROUND: A measles epidemic affected the Nouvelle-Aquitaine region from November 2017 to May 2018 with clusters among Travellers. This indicates that measles vaccination rates among Travellers remain lower than in the general population. The objective of this study was to estimate the 'declarative vaccination' against measles, mumps and rubella (MMR) and to propose a conceptual framework to help identify determinants of MMR vaccination uptake among adult Travellers in Nouvelle-Aquitaine in 2019-20. METHODS: A cross-sectional study using random sampling was performed and included 612 adult Travellers from 1 November 2019 to 31 March 2020. A conceptual framework to model vaccination adherence was tested among this underserved population by using structural equation modelling. This model included five latent variables: health literacy, attitudes toward preventive measures, stigma, accessibility to care and perceived needs and five measured variables: information received on vaccination, perception of barriers, support for administrative documents, social support and housing conditions. RESULTS: Individuals who did not answer all the questions linked to the variables included in the model were excluded, thus 347 adults were included in the final sample. The declared vaccination rate against MMR was 74.0%, and 72.4% of the participants were favorable to vaccination. Vaccination adherence was significantly correlated with favorable attitudes toward preventive measures such as having a history of MMR vaccination and not having already refused a recommended vaccine and finally satisfactory information received on vaccination. DISCUSSION: To improve vaccination adherence, health authorities should lean on personal history with vaccination and on transmitting information on vaccination.

Impact of vaccination against severe COVID-19 in the French population aged 50 years and above: a retrospective population-based study.

BACKGROUND: Given the widespread implementation of COVID-19 vaccination to mitigate the pandemic from the end of 2020, it is important to retrospectively evaluate its impact, in particular by quantifying the number of severe outcomes prevented through vaccination. METHODS: We estimated the number of hospitalizations, intensive care unit (ICU) admissions and deaths directly averted by vaccination in France, in people aged ≥ 50 years, from December 2020 to March 2022, based on (1) the number of observed events, (2) vaccination coverage, and (3) vaccine effectiveness. We accounted for the effect of primary vaccination and the first booster dose, the circulating variants, the age groups, and the waning of vaccine-induced protection over time. RESULTS: An estimated 480,150 (95% CI: 260,072-582,516) hospitalizations, 132,156 (50,409-157,767) ICU admissions and 125,376 (53,792-152,037) deaths were directly averted by vaccination in people aged ≥ 50 years, which corresponds to a reduction of 63.2% (48.2-67.6), 68.7% (45.6-72.4) and 62.7% (41.9-67.1) respectively, compared to what would have been expected without vaccination over the study period. An estimated 5852 (2285-6853) deaths were directly averted among the 50-59 years old, 16,837 (6568-19,473) among the 60-69 years old, 32,136 (13,651-36,758) among the 70-79 years old and 70,551 (31,288-88,953) among the ≥ 80 years old. CONCLUSIONS: The vaccination campaign in France considerably reduced COVID-19 morbidity and mortality, as well as stress on the healthcare system.

SARS-CoV-2 testing, infection and places of contamination in France, a national cross-sectional study, December 2021.

BACKGROUND: This study aimed to describe the use of diagnostic testing for SARS-CoV-2 in France until December 2021, the characteristics of people infected, and places of contamination. METHODS: Data were collected from the national 2021 Health Barometer cross-sectional study, which was conducted between February and December 2021 and included French-speaking individuals aged 18-85 years old selected through randomly generated landline and mobile phone numbers. Participants were interviewed about COVID-19-like symptoms in the previous 12 months, diagnostic testing for SARS-CoV-2, positive diagnosis for SARS-CoV-2, and the place(s) of contamination. Determinants of diagnostic testing and of infection were studied using univariate and multivariate Poisson regressions. RESULTS: A total of 24,514 persons participated in the study. We estimated that 66.4% [65.0-67.7] of persons had been tested for SARS-CoV-2 the last time they experienced COVID-19-like symptoms, and that 9.8% [9.3-10.3] of the population in France - with or without symptoms - had been tested positive. Diagnostic testing was less frequent in men, unemployed persons, and people living alone; it was also less frequent during the first months of the pandemic. The estimated proportion of the population infected was higher in healthcare professionals (PRa: 1.5 [1.3-1.7]), those living in large cities ( > = 200 000 inhabitants, and Paris area) (1.4 [1.2-1.6]), and in households comprising > 3 persons (1.7 [1.5-2.0]). It was lower in retired persons (0.8 [0.6-0.97]) and those over 65 years old (0.6 [0.4-0.9]). Almost two-thirds (65.7%) of infected persons declared they knew where they were contaminated; 5.8% [4.5-7.4] reported being contaminated outdoors, 47.9% [44.8-51.0] in unventilated indoor environments, and 43.4% [40.3-46.6] in ventilated indoor environments. Specifically, 51.1% [48.0-54.2] declared they were contaminated at home or in a family of friend's house, 29.1% [26.4-31.9] at their workplace, 13.9% [11.9-16.1] in a healthcare structure, and 9.0% [7.4-10.8] in a public eating place (e.g., cafeteria, bar, restaurant). CONCLUSIONS: To limit viral spread, preventive actions should preferentially target persons tested least frequently and those at a higher risk of infection. They should also target contamination in households, healthcare structures, and public eating places. Importantly, contamination is most frequent in places where prevention measures are most difficult to implement.

Hepatitis B, C, and delta in the general population in Mayotte: hepatitis B as a major public health concern.

BACKGROUND: Located in southwestern Indian Ocean, Mayotte is a French territory, with a very specific demographic, social and health context. To date, epidemiological data on infections by hepatitis B (HBV), C (HCV), and delta (HDV) viruses in Mayotte have been sparse. We aimed to estimate, in the 15-69-year-old general population living in Mayotte, the prevalence of infections by hepatitis B (HBV), C (HCV), and delta (HDV) viruses and the distribution of HBV status: current infection with positive HBs antigen (Ag); resolved infection with positive HBc antibodies and negative HBsAg; immunisation by vaccination with only positive HBs antibodies; and no infection/no immunisation with negative markers. We also described the characteristics of infected people and assessed the determinants of lifetime HBV infection. METHODS: The Unono Wa Maore survey, implemented in a random sample of the general population in 2018-2019, consisted of an at-home collection of epidemiological data and venous blood samples. Detection of hepatitis B, C, and delta serological and molecular markers was performed. RESULTS: Among 5207 eligible people, 4643 responded to the questionnaire (89.2%), with 2917 being tested for HBV and HCV (62.8%). Estimated HBV status was as follows: current infection 3.0% (95% confidence interval [CI]: 2.3-3.9%) (n = 76); resolved infection 27.8% (95% CI: 25.8-29.9); immunisation by vaccination 27.7% (95% CI: 25.9-29.7); and no infection/no immunisation 41.5% (95% CI: 39.3-43.7). One participant was positive for HDV antibodies (Ab) (0.65%) with a negative HDV-RNA viral load. The risk of lifetime HBV infection was higher in men (adjusted prevalence ratio (aPR): 1.55, 95% CI: 1.29-1.89); in people aged 30-49 years (aPR: 3.83, 95% CI: 1.49-9.81) or 50-69 years (aPR: 4.52, 95% CI: 1.77-11.53) compared to those under 20; in individuals who reported no condom use during their first sexual intercourse (aPR: 1.46, 95% CI: 1.01-2.14); and in those living in Dembeni-Mamoudzou (aPR: 1.40, 95% CI: 1.09-1.80) compared to the West-Centre of Mayotte. Finally, six individuals were positive for HCV antibodies (0.21%), including three positive for HCV RNA. CONCLUSIONS: Mayotte is an area of intermediate endemicity for HBV and low endemicity for HCV and HDV. With a prevalence of HBsAg 10 times higher than in mainland France, a high proportion of people susceptible to HBV infection, and a demographic, health, and social context that may favour its transmission, hepatitis B is a major public health concern in Mayotte.

Influenza vaccination coverage of professionals working in nursing homes in France and related determinants, 2018-2019 season: a cross-sectional survey.

BACKGROUND: The burden of influenza morbidity and mortality in nursing homes (NH) is high. Vaccination of residents and professionals working in NH is the main prevention strategy. Despite recommendations, vaccination coverage among professionals is generally low. METHODS: We performed a nationwide cross-sectional survey of NH using a single-stage stratified random sampling design to estimate influenza vaccination coverage in NH healthcare workers (HCW) and non-medical professionals in France during the 2018-2019 season, and to identify measures likely to increase it. For each NH, a questionnaire was completed with aggregated data by one member of the management team. A multivariate analysis was performed using a negative binomial regression. RESULTS: Five-hundred and eighty nine NH filled in the study questionnaire (response rate: 49.5%). When considering all professionals (i.e., HCW and non-medical professionals), overall vaccination coverage was 30.6% (95%CI [28.2-33.0], range: 1.6-96.2). Overall influenza vaccination coverage in HCW was 31.9% [29.7-34.1]. It varied according to occupational category: 75.5% [69.3-81.7] for physicians, 42.9% [39.4-46.4] for nurses, 26.7% [24.5-29.0] for nursing assistants, and 34.0% [30.1-38.0] for other paramedical personnel. Vaccination coverage was higher i) in private nursing homes (RRa: 1.3, [1.1-1.5]), ii) in small nursing homes (0.9 [0.8-0.9]), iii) when vaccination was offered free of charge (1.4, [1.1-1.8]), iv) when vaccination promotion for professionals included individual (1.6 [1.1-2.1]) or collective (1.3 [1.1-1.5]) information sessions, videos or games (1.4 [1.2-1.6], v) when information on influenza vaccines was provided (1.2 [1.0-1.3], and finally, vi) when a vaccination point of contact-defined as an HCW who could provide reliable information on vaccination-was nominated within the nursing home (1.7 [1.3-2.2]). CONCLUSIONS: Urgent and innovative actions are required to increase coverage in HCW. Vaccination programmes should include free on-site vaccination and education campaigns, and particularly target nursing assistants. The results of this nationwide study provide keys for improving influenza vaccination coverage in HCW. Programmes should ensure that information on influenza vaccines is provided by a vaccination point of contact in NH using attractive media. Combining the different prevention measures proposed could increase coverage in NH nationwide by over 50%.

Cluster of Coronavirus Disease 2019 (COVID-19) in the French Alps, February 2020.

BACKGROUND: On 7 February 2020, French Health authorities were informed of a confirmed case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in an Englishman infected in Singapore who had recently stayed in a chalet in the French Alps. We conducted an investigation to identify secondary cases and interrupt transmission. METHODS: We defined as a confirmed case a person linked to the chalet with a positive reverse-transcription polymerase chain reaction sample for SARS-CoV-2. RESULTS: The index case stayed 4 days in the chalet with 10 English tourists and a family of 5 French residents; SARS-CoV-2 was detected in 5 individuals in France, 6 in England (including the index case), and 1 in Spain (overall attack rate in the chalet: 75%). One pediatric case, with picornavirus and influenza A coinfection, visited 3 different schools while symptomatic. One case was asymptomatic, with similar viral load as that of a symptomatic case. Seven days after the first cases were diagnosed, 1 tertiary case was detected in a symptomatic patient with from the chalet a positive endotracheal aspirate; all previous and concurrent nasopharyngeal specimens were negative. Additionally, 172 contacts were monitored; all contacts tested for SARS-CoV-2 (N = 73) were negative. CONCLUSIONS: The occurrence in this cluster of 1 asymptomatic case with similar viral load as a symptomatic patient suggests transmission potential of asymptomatic individuals. The fact that an infected child did not transmit the disease despite close interactions within schools suggests potential different transmission dynamics in children. Finally, the dissociation between upper and lower respiratory tract results underscores the need for close monitoring of the clinical evolution of suspected cases of coronavirus disease 2019.

Prevalence of hepatitis C infection, screening and associated factors among men who have sex with men attending gay venues: a cross-sectional survey (PREVAGAY), France, 2015.

BACKGROUND: Over the last 20 years, Hepatitis C virus (HCV) infection prevalence has dramatically increased among HIV-infected men who have sex with men (MSM) in many countries worldwide. It is suspected that this increase is primarily driven by sexual behaviours linked to blood exposure. Monitoring these behaviours is crucial to understand the drivers of the epidemic. This study assessed the prevalence of chronic HCV infection among MSM attending gay venues and associated chronic HCV risk factors. HCV screening and associated factors were described. METHODS: The cross-sectional survey PREVAGAY, based on time-location sampling, was conducted in 2015 among MSM attending gay venues in 5 French metropolitan cities. A self-administered questionnaire was completed and capillary whole blood on dried blood spots (DBS) collected. Possible factors associated with chronic HCV prevalence and with HCV screening in the previous year were investigated using Poisson regression. RESULTS: Chronic HCV infection prevalence from DBS analysis was 0.7% [IC95%: 0.3-1.5] in the study's 2645 participants and was 3.0% [1.5-5.8] in HIV-positive MSM. It was significantly higher in those who reported the following: (lifetime) slamming (with or without the sharing of injection equipment); (during the previous year) fisting and chemsex, unprotected anal intercourse with casual partners, using gay websites and/or of mobile-based GPS applications, and having more than 10 sexual partners. Only 41.3% [38.2-44.5] of the participants reported HCV screening during the previous year. Screening was significantly more frequent in MSM under 30 years of age, those who were HIV-positive, those vaccinated against hepatitis B and meningococcus C, and those who reported the following (during the previous year): more than 10 sexual partners, at least one sexually transmitted infection and fisting. CONCLUSION: Chronic HCV infection prevalence in MSM attending gay venues was significantly higher in HIV-positive MSM and in those with risky sexual behaviours. Reflecting current screening recommendations for specific populations, previous HCV screening was more frequent in HIV-positive individuals and those with risky sexual behaviours. Nevertheless, HCV screening coverage needs to be improved in these populations. Comprehensive medical management, which combines screening and linkage to care with prevention strategies, is essential to control HCV among MSM.

Assessment of the impact of the extension of vaccination mandates on vaccine coverage after 1 year, France, 2019.

One year after the extension of the childhood vaccination mandates to the 11 routine vaccinations for children under 2 years old, we estimated vaccination coverage through vaccine reimbursement data. Coverage for children born in 2018 has notably increased. Moreover, vaccine coverage for children and for vaccines not concerned by the law have also shown an increasing trend, supporting a positive impact of the ongoing communication strategy on vaccination, beyond the extension of vaccination mandates.