Dynamic changes in paediatric invasive pneumococcal disease after sequential switches of conjugate vaccine in Belgium: a national retrospective observational study

Review of streptococcus pneumoniae isolates between 2007-2018 in Belgium (during which time 4 different vaccine serotype strategies were used) found that, after a significant decrease during the 13 valent (PCV13) period, the incidence of disease increased during the PCV10 period.

SPS commentary:

Authors highlight that whether changes in epidemiology resulted from the vaccine switch or also from natural evolution remains to be further elucidated.

A related commentary agrees with the study conclusions, that it is difficult to determine whether there is a causal link between the switch to PCV10 and the observed increase in 19A invasive pneumococcal disease. Longer follow-ups would possibly help to prove causality. Also, the effect of PCV10 on the overall burden of invasive pneumococcal disease, rather than serotype-specific invasive pneumococcal disease, is important and should therefore be followed. However, the Belgian National Immunization Technical Advisory Group has decided to switch to PCV13 again, which makes the evaluation of the effect of PCV10 on 19A invasive pneumococcal disease and overall invasive pneumococcal disease burden more complicated.


The Lancet Infectious Diseases

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