The study analysed the incidence of invasive bacterial disease caused by Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis and Streptococcus agalactiae two years before (2018–2019) and during (2020–2021) the pandemic. The researchers analysed disease cases by patient age and serotype or serogroup (variants within species of bacteria that are related to the severity of disease and are the target for vaccine-mediated protection) to assess changes that may have implications for management of the diseases and vaccination programmes.
The stringency of each country’s COVID-19 containment measures was quantified using the Oxford Blavatnik COVID-19 Government Response Tracker. This stringency index combined nine indicators that were tracked daily: school, workplace, and public transport closures; public event cancellations; gathering restrictions; stay at home requirements; internal movement restrictions; international travel controls; and public information campaigns.
Overall, 116,842 cases of invasive disease were analysed in this study: 76,481 pre-pandemic (2018-2019) and 40,360 during the pandemic (2020-2021).
- The number of S. pneumoniae, H. influenzae, and N. meningitidis cases during 2020–21 was approximately half the expected number each year compared to pre-pandemic totals;
- During the pandemic there was a significantly reduced risk of invasive disease caused by S. pneumoniae (relative risk: 0.47; 95% CI: 0.40–0.55), H. influenzae (0.51; 0.40–0.66) and N. meningitidis (0.26; 0.21–0.31). There was no significant change in the risk of invasive disease caused by S. agalactiae (1.02; 0.75–1.40);
- There were no major changes in the overall patterns of disease by patient age or bacterial serotype/serogroup;
- Invasive disease cases began to increase in some countries as pandemic restrictions were lifted;
- Over 36,000 estimated cases of invasive bacterial disease were averted during the first two years of the pandemic in the 30 countries participating in this study.
Dr David Shaw, lead author and DPhil student at Nuffield Department of Population Health, said ‘Our study demonstrates the substantial impact that COVID-19 containment measures had on reducing the transmission of bacterial organisms spread via respiratory droplets. Despite effective vaccines and therapies being available, these organisms pose significant public health challenges and account for a substantial burden of disease globally.