Association of influenza outbreak in each nursery school and community in a ward in Tokyo, Japan

Varicella outbreak at nursery school under routine immunization in Japan in 2017 and 2018 and vaccine effectiveness

BACKGROUND

In Japan, routine administration to one-year-old children of two-dose immunization for varicella was introduced in October 2014. Object The object of this study was to report outbreaks of varicella under routine immunization at a nursery school and in its surrounding area using data of surrounding areas from the (Nursery) School Absenteeism Surveillance System. Then, we measured the effectiveness of routine two-dose immunization for varicella to onset. We tentatively assessed its severity in a nursery school.

METHOD

The study period extended from April 2017 through March 2018. The study area comprised Nursery school B and other nursery schools, and elementary and junior high schools in City A. Subjects in Nursery school B were 120 children. We analyzed vaccine effectiveness (VE) as an observational study and assessed severity using Fisher's exact test. We also assessed VE for severity using linear regression. Severity was defined as the length of nursery school absence attributable to varicella infection.

RESULTS

During the one month preceding a period of two weeks before the initial case at Nursery school B, there were 16 cases of varicella infection in nursery schools, 45 cases in elementary schools, and one case in junior high schools in City A. For children who had received one vaccine dose or more, VE was 48.1% for all ages and 49.2% among children three years old and older. No significant VE against infection was found. Vaccination using one dose or more can reduce severity significantly.

DISCUSSION AND CONCLUSION

Because many nursery school children who had received two doses of vaccine were infected, VE was estimated as low in the nursery school and not significant. Although VE for severity with more than one dose was confirmed, a second dose might not reduce severity compared to one dose.

Nursery school absenteeism surveillance system and infection control measures in nursery schools

INTRODUCTION

The Nursery School Absenteeism Surveillance System (NSASSy), which includes 40% of all nursery schools in Japan, has a degree of effectiveness that is difficult to prove: nursery schools and areas without NSASSy cannot be evaluated for their incidence of infectious diseases as precisely as those with NSASSy. Instead, we examine nursery school countermeasures against infectious diseases by considering the endogeneity bias of NSASSy.

METHOD

After sending questionnaires to 500 Tokyo metropolitan and nearby nursery schools in November 2022, we received their responses through the end of 2022. Questionnaires asked about infection control measures of nursery schools: (1) cooperation with public health centers; (2) cooperation with staff; (3) cooperation with children's parents; (4) precautions among children; (5) countermeasure systems; (6) precaution systems; (7) recording of health conditions of children; (8) usefulness of studying while students; and (9) usefulness of training at nursery schools. Ordered probit with inverse probability weighted adjustment was used as the estimation procedure. The explanatory variable was a dummy variable for using NSASSy. Probability in weight was estimated using the first-step probit for NSASSy. Explanatory variables were a dummy variable for publicly funded nursery schools and a dummy variable for local governments that had adopted NSASSy.

RESULTS

We analyzed 193 nursery schools. NSASSy was negative and associated significantly with (3) cooperation with children's parents and (7) recording of health conditions of children. These countermeasures were more likely to have been taken by NSASSy nursery schools.

"We didn't get much schooling because we were fishing all the time": Potential impacts of irregular school attendance on the spread of epidemics

Objectives

Especially in traditional, rural, and low‐income areas, children attend school irregularly. School‐based interventions are common mitigation strategies for infectious disease epidemics, but if daily attendance is not the norm, the impact of schools on disease spread might be overestimated.

Methods

We use an agent‐based model of an early 20th century Newfoundland community to compare epidemic size and duration in three scenarios: (1) all school‐aged children attend school each weekday, (2) students aged 10–15 have a chance of engaging in adult activities each day, and (3) students aged 10–15 have a chance of being reassigned to adult roles at the start of each simulation and thus never attend school.

Results

As the probability of not attending school increases, epidemics become smaller and peak earlier. The change in final size is larger with permanent reassignment (35% at baseline, 18% at maximum reassignment) than with daily nonattendance (35% vs. 22%). For both scenarios, the peak occurs 3 days earlier with maximum absence compared to the baseline. Benefits extend beyond the reassigned agents, as all school‐aged agents are more likely to escape infection with increasing reassignment, and on average, 3–6 additional agents (2.6%–5.3%) escape infection compared to the baseline.

Conclusions

This study demonstrates that absenteeism can have important impacts on epidemic outcomes. Thus, socioeconomic and other reasons for nonattendance of school, as well as how rates vary in different contexts, must be considered in models predicting epidemic outcomes or evaluating public health interventions in the face of major pandemics.