Epidemiological and clinical characteristics of infections with seasonal human coronavirus and respiratory syncytial virus in hospitalized children immediately before the coronavirus disease 2019 pandemic

Temporal Trends in Respiratory Infection Epidemics Among Pediatric Inpatients Throughout the Course of the COVID-19 Pandemic From 2018 to 2023 in Fukushima Prefecture, Japan

BACKGROUND

Nonpharmaceutical interventions for coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2, during the pandemic altered the epidemiology of respiratory viruses. This study aimed to determine the changes in respiratory viruses among children hospitalized from 2018 to 2023.

METHODS

Nasopharyngeal specimens were collected from children aged under 15 years with fever and/or respiratory symptoms admitted to a medical institution in Fukushima Prefecture between January 2018 and December 2023. Eighteen respiratory viruses were detected using real-time reverse transcription-polymerase chain reaction.

RESULTS

Overall, 1933 patients were included. Viruses were detected in 1377 (71.2%); of these, a single virus was detected in 906 (46.9%) and multiple viruses in 471 (24.3%). Among the viruses whose epidemics were temporarily suppressed, the epidemics of respiratory syncytial virus A and human parainfluenza virus type 3 (HPIV3) started earlier, and the epidemics of human metapneumovirus, HPIV1, and influenza A and C viruses resumed as behavioral restrictions for preventing COVID-19 eased. The median age of children with airway infection was significantly higher in the postpandemic group than in the prepandemic group (18.0 months vs. 21.0 months, p < 0.01). The median age of children infected with HPIV3 and human rhinovirus was significantly higher in the postpandemic group than in the prepandemic group.

CONCLUSIONS

Strengthening of nonpharmaceutical interventions changed the epidemic dynamics of pediatric infectious diseases, with a trend toward older hospitalized children. Continuous monitoring of pediatric infectious disease outbreaks in hospitalized children can help prepare for the emergence of future viruses and pandemics.

Cost-Effectiveness Analysis of Maternal Respiratory Syncytial Virus Vaccine in Protecting Infants from RSV Infection in Japan

INTRODUCTION

Respiratory syncytial virus (RSV) is one of the major causes of respiratory tract infections among children. Until recently, the monoclonal antibody palivizumab was the only RSV prophylaxis available in Japan. In 2024, the bivalent RSV prefusion F protein-based (RSVpreF) vaccine was approved for the prevention of RSV infection in infants by active immunization of pregnant women. In this study, we assessed the cost-effectiveness of a combined strategy of RSVpreF vaccine and palivizumab in Japanese setting.

METHODS

Using a Markov model, we evaluated prevented cases and deaths of medically attended RSV infections from birth to age 11 months for each of the three healthcare settings: inpatient (hospitalization), emergency department visits, and outpatient visits. Incremental cost-effectiveness ratios (ICERs) were calculated from economic outcomes (intervention costs, medication costs, and productivity losses) and quality-adjusted life years (QALYs). Further, we calculated the maximum price of RSVpreF vaccine within which the program would be cost-effective.

RESULTS

In comparison with the current prophylaxis (palivizumab alone), a combined prophylaxis of year-round RSVpreF vaccination of pregnant women and palivizumab prescription for premature infants born in < 32 weeks gestational age (wGA) and all infants with high risk prevented 14,382 medically attended cases of RSV (hospitalization, 7490 cases; emergency department, 2239 cases; outpatient, 4653 cases) and 7 deaths, respectively. From a healthcare payer perspective, when the price of RSVpreF vaccine was equal to or less than ¥23,948 (US $182), a combination prophylaxis was cost-effective under the ICER threshold of ¥5 million per QALY. The other combination prophylaxis of year-round RSVpreF vaccination and palivizumab prescription of premature born in < 32 wGA regardless of risk in infants was a dominant strategy (more effective and less costly).

CONCLUSION

A combined prophylaxis of year-round RSVpreF vaccine and palivizumab could be a cost-effective strategy to protect neonates throughout the infant stage (< 1 years old) in Japan.

Molecular Epidemiology of Human Metapneumovirus in East Japan before and after COVID-19, 2017-2022

Human metapneumovirus (hMPV) is genetically classified into two major subgroups, A and B, based on attachment glycoprotein (G protein) gene sequences. The A2 subgroup is further separated into three subdivisions, A2a, A2b (A2b1), and A2c (A2b2). Subgroup A2c viruses carrying 180- or 111-nucleotide duplications in the G gene (A2c 180nt-dup or A2c 111nt-dup ) have been reported in Japan and Spain. The coronavirus disease 2019 (COVID-19) pandemic disrupted the epidemiological kinetics of other respiratory viruses, including hMPV. In this study, we analyzed the sequences of hMPV isolates in Tokyo and Fukushima obtained from 2017 to 2022, i.e., before and after the COVID-19 pandemic. Subgroup A hMPV strains were detected from 2017 to 2019, and most cases were A2c 111nt-dup, suggesting ongoing transmission of this clade, consistent with global transmission dynamics. Subgroup B viruses, but not subgroup A viruses, were detected in 2022 after the COVID-19 peak. Phylogenetic analysis showed that the subgroup B viruses were closely related to strains detected in Yokohama from 2013 to 2016, and strains detected in Fukushima in 2019, suggesting the reappearance of local endemic viruses in East Japan.

Evidence of the simultaneous replications of active viruses in specimens positive for multiple respiratory viruses

IMPORTANCE

Since the pandemic of coronavirus diseases 2019, the use of real-time PCR assay has become widespread among people who were not familiar with it in virus detection. As a result, whether a high real-time PCR value in one time test indicates virus transmissibly became a complicated social problem, regardless of the difference in assays and/or amplification conditions, the time and number of diagnostic test during the time course of infection. In addition, the multiple positives in the test of respiratory viruses further add to the confusion in the interpretation of the infection. To address this issue, we performed virus isolation using pediatric SARI (severe acute respiratory infections) specimens on air-liquid interface culture of human bronchial/tracheal epithelial cell culture. The result of this study can be a strong evidence that the specimens showing positivity for multiple agents in real-time PCR tests possibly contain infectious viruses.

Impact of the COVID-19 pandemic on the clinical features of pediatric RSV infection in Japan

Background

Mitigation measures implemented during the coronavirus disease 2019 (COVID-19) pandemic remarkably reduced the incidence of infectious diseases among children. However, a reemergence of respiratory syncytial virus (RSV) infection was observed in 2021 in Japan. We compared the clinical characteristics of hospitalized patients with RSV infection before and during COVID-19.

Methods

We retrospectively enrolled children aged <6 years who were hospitalized with RSV infection in 18 hospitals and compared their clinical characteristics before (January 2019 to April 2020, 1,675 patients) and during COVID-19 (September 2020 to December 2021, 1,297 patients).

Results

The mean age of patients with RSV infection was significantly higher during COVID-19 than before (17.4 vs. 13.7 months, P < .001). Compared with before COVID-19, a 2.6-fold increase in RSV cases in the 2–5 years age group was observed from sentinel surveillance during COVID-19, while a 1.2-fold increase was noted in the same age group among hospitalized patients. On average for all patients, consolidation shadows obtained on radiography were less frequently observed (26.1 vs. 29.6%, P = .04) and reduced respiratory assistance (42.2% vs. 48.7%, P < .001) and hospitalization stay (5.7 vs. 6.0 days, P < .001) was required in patients with RSV infection during COVID-19.

Conclusions

COVID-19 and social activity restriction caused epidemiological changes in pediatric RSV infections, and a majority of patients with RSV infection aged ≥2 years did not develop severe symptoms requiring hospitalization. The RSV symptoms during the COVID-19 outbreak were equivalent to or milder than in the previous seasons.