Rapid reduction in invasive pneumococcal disease after introduction of PCV7 into the National Immunization Plan in Israel

Background: The 7-valent conjugated vaccine (PCV7) was introduced into the Israeli National Immunization Program (NIP) in July 2009 (2, 4, 12 months schedule; 2 dose catch-up in second year of life). Nationwide active prospective surveillance on invasive pneumococcal disease (IPD) has been conducted in children since 1989. In the current study, IPD epidemiology in children <5 years during the 20 years before and 18 months after PCV7 NIP initiation, is reported. Methods: All 27 centers performing blood/cerebrospinal fluid (CSF) cultures in children reported monthly IPD cases. Capture-recapture approach was used for completeness. Results: During 1989-2010, 6022 IPD cases were reported in children <5 years; PCV7 serotypes (7VST) caused ∼50% of all episodes. In 2009 and 2010, 7VST IPD incidences <5 years of age (per 100,000) were 15.9 and 5.4, respectively (a 43% and 81% decrease, respectively) compared to 2003-2007 (mean incidence 27.8). Serotype 6A dynamics resembled those of 7VST. The respective overall IPD incidence decreases were 23% and 42%. The incidence dynamics of serotypes 1, 3, 5, 7F and 19A IPD were characterized by considerable fluctuations over the study period without any upwards or downwards trend in any of the age groups. The overall incidence of serotypes not included in the 13-valent pneumococcal conjugate vaccine (PCV13) did not vary significantly during the study period. By the end of 2010, 72% of the remaining IPD was caused by pneumococcal serotypes included in PCV13. Conclusions: An active prospective long-term surveillance, showed a rapid and sharp decline in IPD in children <5 years following initiation of NIP with PCV7. No serotype replacement has been observed so far. The transition from PCV7 to PCV13 initiated in October 2010 may lead to a further substantial decrease in IPD. Follow-up is needed to better determine the long-term PCV effects.