Background: For the scarcity of data, we investigated the vaccine effectiveness (VE) of the combined use of pneumococcal conjugate vaccines (PCVs) of different valences against invasive pneumococcal disease (IPD) in children.
Methods: We conducted a matched case-control study using the national IPD surveillance database and the national vaccination registry. Four age-matched, gender-matched and neighborhood-matched controls were identified for each incident IPD case ≦5 years with disease onsets between October 2007 and December 2013. Conditional logistic regression was used to assess VE against all serotype and serotype 19A IPD.
Results: In 523 cases (median age: 28.5 months; range: 2.0-69.4 months) and 2086 controls (28.7; 2.2-70.1), a similar VE against all-serotype IPD was found between PCV13 (76%; 61-85%) and combined 7-valent PCV (PCV7)/10-valent PCV (PCV10) plus PCV13 (78%; 56-89%). The VE for PCV7/PCV10 was slightly lower (48%; 32-60%). Regarding serotype 19A, a significantly reduced risk was observed for both PCV13 (82%; 63-91%) and combined PCV7/PCV10 plus PCV13 (87%; 61-96%). PCV7/PCV10 had only a borderline protective association (31%; 4-51%). For children receiving PCV13 alone, VE against all-serotype IPD did not differ between starting the dosing at ≥2 (78%; 56-89%) or <2 (74%; 51-87%) years of age. VE was 81% (69-88%) within 6 months of the last dose of PCV and 19% (95% CI: -21 to 45%) after 2 years.
Conclusions: PCVs are effective against IPD during immunization with either the same or with a mixed series, but protection might be differential over time.