Table 1.

Rationale for selection of S. pneumoniae strains based on epidemiological relevance.

Serotype	PCV13 serotype	Observations	References
3	Yes	High invasive disease potential Increasing in PCV13 era	(Sá-Leão et al., 2011; Horácio et al., 2016)
15A	No	Increasing in carriage in PCV13 era	(Félix et al., 2021)
19A	Yes	Highly prevalent in carriage and disease before the introduction of PCV13	(Isturiz et al., 2017)
19F	Yes	Remains in carriage in PCV13 era	(Nunes et al., 2016; Félix et al., 2021)
22F; 33F	No	Increasing in carriage in PCV13 era Important cause of invasive pneumococcal disease Targeted by upcoming PCV15 and PCV20 vaccines	(Moore et al., 2015; Félix et al., 2021)
NT	No	Non-encapsulated Very frequent in colonization Frequently detected in co-colonization Associated with multidrug resistance Associated to conjunctivitis outbreaks	(Marks et al., 2012; Valentino et al., 2014; Valente et al., 2016b)

PCV13, PCV15 and PCV20 correspond to 13-valent, 15-valent and 20-valent pneumococcal conjugate vaccines. NT - non-typeable.