Impacts of routine varicella vaccination program and COVID-19 pandemic on varicella and herpes zoster incidence and health resource use among children in Japan.

PURPOSE

To determine the epidemiological trends in pediatric varicella and herpes zoster incidence and changes in healthcare resource use from 2005 to 2022 using a nationally representative database in Japan.

MATERIALS AND METHODS

We conducted a retrospective observational study consisting of 3.5 million children with 177 million person-months during 2005-2022 using Japan Medical Data Center (JMDC) claims database in Japan. We investigated trends in incidence rates of varicella and herpes zoster and changes in healthcare resource use (e.g., antiviral use, office visits, and healthcare costs) over 18 years. Interrupted time-series analyses were used to investigate the impact of the routine varicella vaccination program in 2014 and infection prevention measures against COVID-19 on incidence rates of varicella and herpes zoster and related healthcare utilization.

RESULTS

After the introduction of the routine immunization program in 2014, we observed level changes in incidence rates (45.6 % reduction [95 %CI, 32.9-56.0] of varicella cases, antiviral use (40.9 % reduction [95 %CI, 25.1-53.3]), and relevant healthcare costs (48.7 % reduction [95 %CI, 38.2-57.3]). Furthermore, infection prevention measures against COVID-19 were associated with additional level changes in varicella rates (57.2 % reduction [95 %CI, 44.5-67.1]), antiviral use (65.7 % reduction [59.7-70.8]), and healthcare costs (49.1 % [95 %CI, 32.7-61.6]). In contrast, the changes in incidence and healthcare costs for herpes zoster were relatively small, which showed 9.4 % elevated level change with a decreasing trend and 8.7 % reduced level change with a decreasing trend after the vaccine program and the COVID-19 pandemic. The cumulative incidence of herpes zoster in children born after 2014 was lower than that before 2014.

CONCLUSIONS

Varicella incidence and healthcare resource use were largely affected by the routine immunization program and infection prevention measures against COVID-19, while these impacts on herpes zoster were relatively small. Our study indicates that immunization and infection prevention measures largely changed pediatric infectious disease practices.