Thomas Althaus

Background: Resistance of the arbovirus vector Aedes albopictus to pyrethroid insecticides is an emerging threat to vector control programs in Europe. Three knock-down resistance (’ Kdr ’) mutations affecting the voltage-gated sodium channels targeted by pyrethroids are known to confer resistance: V1016G, I1532T and F1534C . As these Kdr mutations are actively circulating in Europe, their monitoring is crucial for resistance surveillance programs. However, current Kdr genotyping methods are labor-intensive and costly, limiting their applicability for large-scale high-throughput surveillance. Methodology: Novel digital droplet PCR (ddPCR) TaqMan assays were developed, allowing the quantification of these Kdr mutations from pooled mosquito samples from field populations. The specificity of these assays was validated by using mosquitoes of known genotypes together with synthetic DNA constructs carrying haplotype combinations previously unseen in the field. The assays’ accuracy was assessed by comparing Kdr frequencies measured from pooled mosquitoes to those derived from individual genotypes. These assays were then used in a pilot surveillance study in mainland France, integrating deltamethrin bioassays, pooled Kdr mutation tracking and vector control interventions data. Findings: The developed ddPCR assays demonstrated high accuracy and specificity, with matching Kdr mutation frequencies between pooled samples and individual genotyping. The pilot surveillance study confirmed the low prevalence of Kdr V1016G and I1532T mutations in most French populations, though some populations exhibited a moderate decrease in susceptibility to deltamethrin. Deltamethrin spraying intensity was weakly correlated with Kdr I1532T mutation frequency while no correlation was observed with deltamethrin susceptibility, suggesting that insecticide selective pressure from curative vector control activities is at most a minor driver of resistance. Conclusion: These novel ddPCR assays provide a simple, cost-effective and high-throughput method for quantifying the frequency of Kdr mutations in Ae. albopictus populations. Their implementation in routine country-wide surveillance programs will enhance the detection of emerging resistance, and inform vector control strategies, preventing arboviral disease transmission. Author summary: Aedes albopictus , the Asian tiger mosquito, is an emerging global threat due to its ability to transmit the dengue, chikungunya and Zika viruses among others. Recurrent use of insecticides to prevent infections selects resistant mosquitoes. Kdr (knock-down resistance) mutations confer resistance to pyrethroid insecticides, like deltamethrin. In order to track the arrival of these mutations in a population, individual PCR tests are routinely used, which is very inefficient and costly. The digital droplet PCR tests presented in this study can instead be performed on pools of mosquitoes from the field, greatly increasing the output while reducing the costs. This makes them ideal for use in the surveillance of these mutations in field populations. We first confirmed that the tests are as efficient in pools as they are on single mosquitoes, then we applied these tests in a pilot study on French field mosquitoes to demonstrate their applicability for use in surveillance. Finally, we explored the link between deltamethrin sprayings, bioassay mortality and Kdr mutations frequency, which is non-existent. This means the current management of mosquito populations via insecticide use is sensible. We believe these tests have a place in streamlining the future surveillance programs of these mutations in the field.

Background: Neutralising antibodies (nAbs) are established correlates of protection against severe SARS-CoV-2 outcomes. Their role in preventing mild or asymptomatic infections remains uncertain, particularly across successive variant waves. We assessed whether nAb levels were associated with subsequent SARS-CoV-2 infection, in a nationwide cohort.Methods: The Monaco COVID-19 Public Health Program provided free diagnostic testing, vaccination and serological follow-up in a community setting. Participants of all ages were followed up every six months between July 2021 and March 2023. Incident infections between visits were identified by RT-PCR or antigen testing, anti-N seroconversion, or predicted by random forest analysis. Analyses were stratified by prior infection status and variant period. Mixed-effects logistic regression models evaluated associations between nAb levels and infection.Findings: Among 8,704 participants, 3,727 were infection-naïve at baseline, with 2,347 infections recorded over 18 months. During the delta/omicron period, nAbs were linearly associated with lower infection odds (OR 0.91 [95%CI 0.88–0.94] per 100 IU/mL). During the omicron period, the association was non-linear: nAbs 900 IU/mL conferred significant protection (p=0.03).Among 1,173 previously infected participants, 407 reinfections occurred. Reinfection odds were reduced in those with nAb>900IU/mL during the delta/omicron period (p=0.02) and showed a linear inverse association during the omicron period (OR 0.83 [95%CI 0.79–0.87] per 100 IU/mL). During the delta/omicron period, 57% of infections in naïve participants and 35% in previously infected participants might have been prevented if all had nAbs >800 IU/mL; during the omicron period, 19% and 17%, respectively, for nAbs >900 IU/mL.Interpretation: Higher nAb levels were independently associated with lower odds of SARS-CoV-2 infection across variant periods and infection histories. Monitoring nAbs may inform public health strategies and identify population groups who could benefit most from booster vaccination.

Providing non-invasive, accurate and affordable SARS-CoV-2 tests represents a public health priority, to better control the spread of the virus while protecting healthcare workers. Saliva is a robust alternative to nasopharyngeal (NP) swabs, but there is heterogeneity in collection and pre-analytical methods. Relying on a national COVID-19 Public Health Programme, we prospectively recruited 3,488 symptomatic and asymptomatic adults attending the Monaco community centre for NP RT-PCR testing from February 2021–2023. Saliva was concomitantly obtained with either a buccal swab or an oral sponge (OS) and analysed by an RT-PCR assay and a fully automated electrochemiluminescence enzyme immunoassay (ECLIA) rapid antigen test (RAT). The sensitivity of the buccal RT-PCR varied according to previous SARS-CoV-2 infection, vaccination, and the presence of symptoms, while it remained around 95% for the OS RT-PCR. The specificity of the buccal RT-PCR approached 100% and was around 95% for the OS-RT PCR. The RAT sensitivity was 66.9% and 69.1% compared to NP and OS RT-PCR assays and increased to 71% and 97% in case of a high viral load (Ct < 25), respectively. RT-PCR assay using OS saliva showed high accuracy in symptomatic and non-symptomatic adults, including the identification of negative nasopharyngeal swabs. This method allows self-collection without any prior conditions for the patient nor laboratory pre-analytical steps. The ECLIA RAT offers high throughput but is only useful in individuals with high viral loads. Our findings encompassed the latest SARS-CoV-2 omicron subvariants, such as BA.4&5 and the XBB series. Registry: ClinicalTrials.gov. Registration number: NCT05074745. Registration date: 12-10-2021.

Background: We quantified SARS-CoV-2 dynamics in different community settings and the direct and indirect effect of the BNT162b2 mRNA vaccine in Monaco for different variants of concern (VOC). Methods: Between July 2021 and September 2022, we prospectively investigated 20,443 contacts from 6320 index cases using data from the Monaco COVID-19 Public Health Programme. We calculated secondary attack rates (SARs) in households (n = 13,877), schools (n = 2508) and occupational (n = 6499) settings. We used binomial regression with a complementary log–log link function to measure adjusted hazard ratios (aHR) and vaccine effectiveness (aVE) for index cases to infect contacts and contacts to be infected in households. Results: In households, the SAR was 55% (95% CI 54–57) and 50% (48–51) among unvaccinated and vaccinated contacts, respectively. The SAR was 32% (28–36) and 12% (10–13) in workplaces, and 7% (6–9) and 6% (3–10) in schools, among unvaccinated and vaccinated contacts respectively. In household, the aHR was lower in contacts than in index cases (aHR 0.68 [0.55–0.83] and 0.93 [0.74–1.1] for delta; aHR 0.73 [0.66–0.81] and 0.89 [0.80–0.99] for omicron BA.1&2, respectively). Vaccination had no significant effect on either direct or indirect aVE for omicron BA.4&5. The direct aVE in contacts was 32% (17, 45) and 27% (19, 34), and for index cases the indirect aVE was 7% (− 17, 26) and 11% (1, 20) for delta and omicron BA.1&2, respectively. The greatest aVE was in contacts with a previous SARS-CoV-2 infection and a single vaccine dose during the omicron BA.1&2 period (45% [27, 59]), while the lowest were found in contacts with either three vaccine doses (aVE − 24% [− 63, 6]) or one single dose and a previous SARS-CoV-2 infection (aVE − 36% [− 198, 38]) during the omicron BA.4&5 period. Conclusions: Protection conferred by the BNT162b2 mRNA vaccine against transmission and infection was low for delta and omicron BA.1&2, regardless of the number of vaccine doses and previous SARS-CoV-2 infection. There was no significant vaccine effect for omicron BA.4&5. Health authorities carrying out vaccination campaigns should bear in mind that the current generation of COVID-19 vaccines may not represent an effective tool in protecting individuals from either transmitting or acquiring SARS-CoV-2 infection.

Objective: Critical gaps remain in understanding community perceptions and treatment‐seeking behaviours in case of fever. This is especially relevant considering global antimicrobial resistance, where fever is assumed to provoke non‐judicious antibiotic use. Our study objective was therefore to document the community‐level incidence of fever, the resulting treatment‐seeking processes, and their underlying behavioural drivers.Methods: In a cross‐sectional observational design, we used descriptive and inferential statistics and multivariable regression analysis to estimate the population‐level incidence of fever and individual and socio‐economic factors associated with treatment‐seeking process characteristics. We utilised a detailed publicly available survey of community‐level treatment‐seeking behaviour (collected in 2017/2018), comprising a representative sample of 2130 rural adults in Thailand (Chiang Rai Province) and Lao PDR (Salavan Province).Results: Fever was reported by 7.1% of the rural adult population in Chiang Rai (95% CI: 5.1%–9.0%) and 7.5% in Salavan (95% CI: 4.5%–10.5%) during a 2‐month recall period. Treatment‐seeking patterns varied by socio‐economic characteristics like precarious employment. 69.3% (95% CI: 60.8%–77.7%) of fever episodes involved access to formal (public/private) healthcare providers, 11.0% (95% CI: 4.5%–17.5%) involved informal providers, and 24.3% (95% CI: 16.6%–32.1%) took place without either formal or informal healthcare access. Febrile patients had on average 0.39 antibiotic use episodes when accessing formal healthcare settings, compared to 0.05 otherwise (p < 0.01).Conclusion: Treatment‐seeking behaviour during fever varies according to population characteristics. Clinical studies would benefit from contextualising quantitative outcomes. Treatment algorithms for non‐malarial febrile illnesses should involve outreach to informal healthcare and community settings to support patients in precarious circumstances, and antibiotic resistance interventions should prioritise formal healthcare facilities.

Neutralising antibodies (nAbs) play a critical role in the protection against severe COVID-19. In the era of vaccine boosters and repeated SARS-CoV-2 outbreaks, identifying individuals at risk represents a public health priority. Relying on the Monaco COVID Public Health Programme, we evaluated nAbs from July 2021-June 2022 in 8,080 SARS-CoV-2 vaccinated and/or infected children and adults, at their inclusion visit. We stratified by infection status and investigated variables associated with nAbs using a generalised additive model. Infected and vaccinated participants had high and consistent nAbs (>800 IU/mL), which remained stable over time since injection, regardless of the number of vaccine doses, body mass index, sex, or age. By contrast, uninfected participants showed larger variability (two doses [V2] median 157.6; interquartile range [IQR] 43.3-439.1 IU/mL) versus three doses [V3] median 882.5; [829.5-914.8] IU/mL). In the multivariate model, nAbs decreased by 20% per month after V2 (adjusted ratio 0.80; 95%CI [0.79-0.82]), but remained stable after V3 (adjusted ratio 0.98; 95%CI [0.92-1.05]). Hybrid immunity provided stable, high and consistent nAbs over time. The benefit of boosters was marked to restore decaying nAbs in uninfected participants. NAbs could identify individuals at risk of severe COVID-19 and provide more targeted vaccine boosters’ campaigns.

C-reactive protein (CRP) point-of-care testing can reduce antibiotic prescribing in primary care patients with febrile and respiratory illness, yet little is known about its effects on treatment-seeking behavior. If patients go on to source antibiotics elsewhere, the impact of CRP testing will be limited. A randomized controlled trial assessed the impact of CRP testing on antibiotic prescriptions in Myanmar and Thai primary care patients with a febrile illness. Here we report patients’ treatmentseeking behavior before and during the twoweek study period. Self-reported antibiotic use is compared against urine antibacterial activity. Patients’ opinions towards CRP testing were evaluated. Antibiotic use before study enrolment was reported by 5.4% while antimicrobial activity was detected in 20.8% of samples tested. During the study period, 14.8% of the patients sought additional healthcare, and 4.3% sourced their own antibiotics. Neither were affected by CRP testing. Overall, patients’ satisfaction with their care and CRP testing was high. CRP testing did not affect patients’ treatment-seeking behavior during the study period whilst modestly reducing antibiotic prescriptions. CRP testing appears to be acceptable to patients and their caregivers.

The French and Italian Riviera are one of the most important areas in the world for yachting and cruise activity. Even though ports and airports of this area make up a single network, they insist on the territory of two different EU countries (Italy and France), and of one non-EU (Principality of Monaco), that have different health systems and legislations. In this context, a collaboration between maritime port health authorities became essential to perform an effective public health action in order to prevent the spread of infectious diseases. In this paper are illustrated the best practices in the domain of maritime public health collaboration between Italy and Monaco during the Covid-19 pandemic, and programs for future developments that should be a benchmark for other cooperation programs between eropean health port authorities.

This article presents the findings of a national retrospective cohort comparing pre-Omicron and Omicron periods in over 18,000 children and adolescents in Qatar, matched by age, sex, nationality, and co-existing conditions. Vaccine effectiveness (BNT162b2, 10µg) on SARS-CoV-2 Omicron infection was as low as 25.7% and negligible three months after vaccination. Adolescents received a 30µg vaccine, showing vaccine effectiveness of 30.6% in the Omicron period, also waning over time. I found this article relevant to demonstrate that the BNT162b2 vaccine should not be used to stop viral transmission in healthy children. Future research on new COVID vaccines interrupting viral transmission is warranted.