A new paradigm in pneumococcal conjugate vaccination: moving from individual to herd protection

July 30, 2017 at 12:44 pm

International Journal of Infectious Diseases July 2017 V.60 N.7 P.96-97


Gail L. Rodgers, Keith P. Klugman

Immunization programs incorporating pneumococcal conjugate vaccines (PCV) have led to a dramatic decrease in invasive pneumococcal disease (IPD) due to vaccine serotypes, pneumonia, and otitis media in children receiving these vaccines. Consistent with the conjugate Haemophilus influenzae type B vaccine (Hib) experience (Moulton et al., 2000), decreased nasopharyngeal (NP) carriage resulting in decreased transmission and the herd or indirect effect (decrease in disease in the unvaccinated) has also been seen with PCV, but the magnitude of this benefit has far surpassed initial expectations (Lexau et al., 2005, Pilishvili et al., 2010, Moore et al., 2015, Von Gottberg et al., 2014). Two years following the introduction of PCV7 into the routine vaccination program in the USA using a 3 + 1 schedule (three infant doses at 2, 4, and 6 months of age and one toddler dose at 12–15 months of age), a profound effect was found in the unvaccinated: PCV7 prevented more than twice as many invasive cases through indirect effects than through its direct effect of protecting vaccinated children (CDC, 2005). This has been documented in other countries, including those using reduced dosing schedules such as 2 + 1, as well as in countries using the extended serotype vaccines, PCV10 and PCV13 (Shiri et al., 2017). A reduction in NP carriage of vaccine serotypes, a precursor of the herd effect, was documented in the original 3 + 0 study of conjugate vaccination of infants in Africa (Mbelle et al., 1999) and was confirmed in countries using 3 + 0 schedules (Hammitt et al., 2014). The mechanism for protection in the unvaccinated is due to the decrease and/or near elimination of vaccine serotypes from the nasopharynx. This in turns leads to decreased transmission of these serotypes and decreased disease. Thus, the effect on NP carriage, a non-disease state and critical precursor to disease, is key to the control of pneumococcal disease in countries unlikely to have immunization programs able to immunize all of their children.





Entry filed under: Bacterias, Epidemiología, Infecciones respiratorias, Inmunizaciones, REPORTS, Update.

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