Vaccination of young Gambian children against the pneumococcus bacterium reduced the carriage of vaccine-type pneumococci not only in vaccinated children but also in nonvaccinated older children and adults, reports an international team of researchers (Roca A et al. PLoS Med. 2011;8:e1001107).
In a cluster randomized trial involving 21 rural villages in western Gambia, all residents in the intervention villages received the 7-valent pneumococcal conjugate vaccine; in the control villages, only children younger than 30 months received the vaccine. The prevalence of nasopharyngeal carriage of vaccine-type pneumococcal serotypes was reduced in both the intervention and control villages in all age groups, revealing a potential herd effect from vaccination of young children. Vaccinating an entire village did not lead to an increase in non–vaccine-type strains for 2 years after vaccination.
Friedrich MJ. Community Protection From Pneumococcus Infection. JAMA. 2011;306(23):2553. doi:10.1001/jama.2011.1806