Increase in invasive disease caused by Haemophilus influenzae b, the Netherlands, 2020 to 2021

The incidence of most respiratory-transmitted diseases decreased during the COVID-19 pandemic as a result of containment measures. In contrast, in the Netherlands we noted an increase in invasive disease caused by Haemophilus influenzae b (Hib) (from t 0.3/100,000 before 2019 to 0.39 and 0.33/100,000 in 2020 and 2021) in vaccinated and unvaccinated age groups. We did not find a change in vaccine effectiveness against Hib invasive disease (effectiveness > 90%). We discuss factors that may have contributed to this rise.

Automated summary

While the incidence of most respiratory-transmitted diseases decreased during the COVID-19 pandemic, there was an increase in invasive disease caused by Haemophilus influenzae b (Hib) in the Netherlands, affecting both vaccinated and unvaccinated age groups. The vaccine effectiveness against Hib invasive disease remained unchanged, with a high effectiveness rate exceeding 90%. Various factors contributing to this rise in invasive disease were discussed.