Reduction of Carriage and Transmission of Streptococcus pneumoniae: The Beneficial “Side Effect” of Pneumococcal Conjugate Vaccine

摘要

In 2000, the 7‐valent polysaccharide pneumococcal conjugate vaccine (PCV7) was recommended in the United States for routine use in all infants and children aged <2 years and in high‐risk children aged 4 years [1]. Several controlled clinical trials have shown that the vaccine is highly efficacious in preventing invasive pneumococcal disease (IPD) in vaccinated children. The incidence of vaccine‐type IPD among children aged <5 years decreased 94% from 1998 to 2003 [2] and plateaued in 2002–2005 [3]. Use of the vaccine also reduced the incidence of IPD among unvaccinated populations. In fact, from 1998 to 2003, the incidence of vaccine‐type IPD decreased up to 60% among persons aged >5 years [2–4], and a statistically significant decrease of 40% among infants too young to be vaccinated was also found [5]. These data suggest a key role for indirect effects of PCV7, and it has been suggested that both reduction in nasopharyngeal carriage and reduction in transmission of vaccine‐type pneumococci could be possible mechanisms of herd immunity to Streptococcus pneumoniae.