Decline in respiratory deaths not associated with influenza in Russia: effect of the introduction of the pneumococcal conjugate vaccine (PCV13), or improvement in care?

Background Pneumococcal vaccination (PCV13) for children (as well as older adults) in Russia was introduced in 2014, with no prior PCV7 use. While pneumonia hospitalization rates, both in children and adults didn’t decrease in the following years, respiratory mortality rates declined with time. Moreover, there is a strong association between antibiotic, including multidrug resistance and PCV13 vaccine serotypes for S. pneumoniae in children in Russia, and presence of S. pneumoniae among sepsis cases in Russia during the recent years has been very low. Annual variability in influenza circulation may affect some of the changes in respiratory mortality rates, obscuring the trends in respiratory mortality related to pneumococcal vaccination. Methods We applied the inference method from our recent study of influenza-associated mortality in Russia to relate monthly respiratory mortality rates between 09/2010 and 08/2019 to monthly indices of influenza circulation and baseline rates of mortality not associated with influenza, allowing for a potential trend in the baseline rates starting 2015. Results Baseline rates of respiratory mortality not associated with influenza decreased with time starting from the 2014/15 season (with each season running from September to August), with the 2018/19 baseline rates of respiratory mortality per 100,000 individuals being lower by 12.41 (95% CI (10.6,14.2)) compared to the 2010-2014 period. Conclusions While improvement in care might have contributed to the reduction in the rates of respiratory mortality not associated with influenza in Russia, the above temporally consistent reduction is compatible with the gradual replacement of vaccine serotypes in the transmission and carriage of S. pneumoniae following the introduction of PCV13. Further work is needed to better understand the impact of PCV13 on the epidemiology of respiratory infections and related mortality in Russia.