ABSTRACT
IMPORTANCEDuring the COVID-19 pandemic children and adolescents were massively infected worldwide. In 2022 reinfections became increasingly common and they may continue to be a main feature of the endemic phase of SARS-CoV-2. It is important to understand the epidemiology and clinical impact of reinfections. OBJECTIVETo assess the incidence, risk, and severity of SARS-CoV-2 reinfection in children and adolescents. DESIGN, SETTING, AND PARTICIPANTSA population-level observational study was performed using surveillance data from the Autonomous Province of Vojvodina, Serbia between March 6, 2020 and April 30, 2022 with follow-up until July 31, 2022. The population-based sample consisted of 32 524 residents of Vojvodina <18 years of age with laboratory confirmed SARS-CoV-2 infection. EXPOSURESThe surveillance database of the Institute for Public Health of Vojvodina was harnessed for epidemiological data of laboratory-confirmed SARS-CoV-2 infections. MAIN OUTCOMES AND MEASURESIncidence rates of documented SARS-CoV-2 reinfection per 1000 person-months. Estimated risk of documented reinfection [≥]90 days after laboratory confirmation of primary infection. Reinfection severity and associated hospitalizations and deaths. RESULTSA total of 964 children (3.0%) experienced documented reinfection. The incidence rate of SARS-CoV-2 documented reinfections was 3.2 (CI 3.0-3.4) cases per 1000 person-months and was highest in adolescents aged 12-17 years (3.4; CI 3.2-3.7). Most reinfections (905, 93.9%) were recorded in 2022. The reinfection risk was 1.3% at six months, 1.9% at nine months, 4.0% at 12 months, 6.7% at 15 months, 7.2% at 18 months and 7.9% after 21 months. Pediatric COVID-19 cases were generally mild. The proportion of severe clinical forms decreased from 14 (1.4%) in initial episodes to 3 (0.3%) in reinfections. Reinfected children were 4.7 times more likely to suffer from severe disease during initial infection compared to reinfection (McNemar OR=4.7; 95%CI 1.3-16.2, p=0.015). Pediatric reinfections rarely led to hospitalization (0.5% vs. 1.3% during primary infections) and none resulted in death. CONCLUSION AND RELEVANCEReinfections are becoming more frequent as the pandemic progresses, yet the risk remains substantially lower for children and adolescents compared to adults. Pediatric infections rarely had clinical consequences and reinfections were even milder than primary infections. Key PointsO_ST_ABSQuestionC_ST_ABSWhat is the incidence, risk and severity of SARS-CoV-2 reinfection in children and adolescents? FindingsThis observational population-level study showed that the risk of pediatric reinfection remained less than 8% two years into the pandemic with an incidence rate of 3.2 (CI 3.0-3.4) cases per 1000 person-months. Pediatric COVID-19 cases were generally mild and reinfected children were 4.7 times more likely to suffer from severe disease during the initial infection compared to reinfection. MeaningThese findings suggest that documented reinfection risk remains substantially lower in the pediatric versus the adult population, with an even more favorable profile compared to primary infections.
ABSTRACT
BackgroundData on the rate and severity of SARS-CoV-2 reinfections in real-world settings are scarce and the effects of vaccine boosters on reinfection risk are unknown. MethodsIn a retrospective cohort study, registered SARS-CoV-2 laboratory-confirmed Vojvodina residents, between March 6, 2020 and October 31, 2021, were followed for reinfection [≥]90 days after primary infection. Data were censored at the end of follow-up (January 31, 2022) or death. The reinfection risk was visualized with Kaplan-Meier plots. To examine the protective effect of vaccination, the subset of individuals with primary infection in 2020 (March 6-December 31) were matched (1:2) with controls without reinfection. FindingsUntil January 31, 2022, 13,792 reinfections were recorded among 251,104 COVID-19 primary infections (5.49%). Most reinfections (86.8%) were recorded in January 2022. Reinfections were mostly mild (99.2%). Hospitalizations were uncommon (1.8% vs. 3.70% in primary infection) and COVID-19 deaths were very rare (n=20, case fatality rate 0.15%). The overall incidence rate of reinfections was 5.99 (95% CI 5.89-6.09) per 1,000 person-months. The reinfection risk was estimated as 0.76% at six months, 1.36% at nine months, 4.96% at 12 months, 16.7% at 15 months, and 18.9% at 18 months. Unvaccinated (OR=1.23; 95%CI=1.14-1.33), incompletely (OR=1.33; 95%CI=1.08-1.64) or completely vaccinated (OR=1.50; 95%CI=1.37-1.63), were modestly more likely to be reinfected compared with recipients of a third (booster) vaccine dose. InterpretationSARS-CoV-2 reinfections were uncommon until the end of 2021 but became common with the advent of Omicron. Very few reinfections were severe. Boosters may modestly reduce reinfection risk.
ABSTRACT
Molecular epidemiology has provided an additive value to traditional public health tools by identifying SARS-CoV-2 clusters, or providing evidence that clusters based on virus sequences and contact tracing are highly concordant. Our aim was to infer the levels of virus importation and to estimate the impact of public health measures related to travel restrictions to local transmission in Greece. Our phylogenetic and phylogeographic analyses included 389 SARS-CoV-2 sequences collected during the first 7 months of the pandemic in Greece and a random collection in 5 replicates of 3,000 sequences sampled globally, as well as the best hits to our dataset identified by BLAST. Phylogenetic analyses revealed the presence of 70 genetically distinct viruses identified as independent introductions into Greece. The proportion of imported strains was 41%, 11.5%, and 8.8% during the three periods of sampling, namely, March (no travel restrictions), April to June (strict travel restrictions), and July to September (lifting of travel restrictions based on a thorough risk assessment), respectively. These findings reveal low levels of onward transmission from imported cases during summer and underscore the importance of targeted public health measures that can increase the safety of international travel during a pandemic.
ABSTRACT
SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is a novel Coronavirus responsible for the Coronavirus Disease-2019 (COVID-19) pandemic. Since the beginning of the pandemic, the virus has spread in almost the entire world. Tracing and tracking virus international and local transmission has been an enormous challenge. Chains of infections starting from various countries worldwide seeded the outbreak of COVID-19 in Athens, capital city of Greece. Full-genome analysis of isolates from Athens Hospitals and other healthcare providers revealed the variety of SARS-CoV-2 that initiated the pandemic before lock-down and passenger flight restrictions. The present work may serve as reference for resolving future lines of infection in the area and Europe especially after resumption of passenger flight connections to Athens and Greece during summer of 2020.
ABSTRACT
Since the first suspected case of coronavirus disease-2019 (COVID-19) on December 1st, 2019, in Wuhan, Hubei Province, China, a total of 40,235 confirmed cases and 909 deaths have been reported in China up to February 10, 2020, evoking fear locally and internationally. Here, based on the publicly available epidemiological data for Hubei, China from January 11 to February 10, 2020, we provide estimates of the main epidemiological parameters. In particular, we provide an estimation of the case fatality and case recovery ratios, along with their 90% confidence intervals as the outbreak evolves. On the basis of a Susceptible-Infected-Recovered-Dead (SIDR) model, we provide estimations of the basic reproduction number (R0), and the per day infection mortality and recovery rates. By calibrating the parameters of the SIRD model to the reported data, we also attempt to forecast the evolution of the of the outbreak at the epicenter three weeks ahead, i.e. until February 29. As the number of infected individuals, especially of those with asymptomatic or mild courses, is suspected to be much higher than the official numbers, which can be considered only as a subset of the actual numbers of infected and recovered cases in the total population, we have repeated the calculations under a second scenario that considers twenty times the number of confirmed infected cases and forty times the number of recovered, leaving the number of deaths unchanged. Based on the reported data, the expected value of R0 as computed considering the period from the 11th of January until the 18th of January, using the official counts of confirmed cases was found to be [~]4.6, while the one computed under the second scenario was found to be [~]3.2. Thus, based on the SIRD simulations, the estimated average value of R0 was found to be [~] 2.6 based on confirmed cases and2 based on the second scenario. Our forecasting flashes a note of caution for the presently unfolding outbreak in China. Based on the official counts for confirmed cases, the simulations suggest that the cumulative number of infected could reach 180,000 (with lower bound of 45,000) by February 29. Regarding the number of deaths, simulations forecast that on the basis of the up to the 10th of February reported data, the death toll might exceed 2,700 (as a lower bound) by February 29. Our analysis further reveals a significant decline of the case fatality ratio from January 26 to which various factors may have contributed, such as the severe control measures taken in Hubei, China (e.g. quarantine and hospitalization of infected individuals), but mainly because of the fact that the actual cumulative numbers of infected and recovered cases in the population most likely are much higher than the reported ones. Thus, in a scenario where we have taken twenty times the confirmed number of infected and forty times the confirmed number of recovered cases, the case fatality ratio is around [~] 0.15% in the total population. Importantly, based on this scenario, simulations suggest a slow down of the outbreak in Hubei at the end of February.
