PCV7

PCV7, or seven-valent pneumococcal conjugate vaccine, is a vaccine designed to protect against invasive disease caused by seven serotypes of Streptococcus pneumoniae. The vaccine includes capsular polysaccharides from serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F conjugated to a protein carrier, commonly a component of diphtheria toxin, which enhances the immune response in infants.

Developed by Wyeth and first licensed in the United States in 2000, PCV7 was introduced into routine childhood immunization schedules in many countries. The standard infant schedule typically involves doses at 2, 4, and 6 months, with a booster dose at 12 to 15 months, though exact timing varies by country.

Effectiveness studies showed substantial declines in invasive pneumococcal disease caused by vaccine serotypes following introduction, as well as reduced nasopharyngeal carriage of those serotypes and indirect protection (herd immunity) in unvaccinated groups.

However, vaccination with PCV7 led to shifts in pneumococcal populations, with increases in disease caused by non-vaccine serotypes, a phenomenon known as serotype replacement; most notably, increases in serotypes not covered by PCV7 were observed in some settings.

Safety data generally indicated a favorable profile, with common adverse events including injection-site pain or redness and fever; severe adverse events were rare.

With the development of higher-valency pneumococcal vaccines, PCV7 has been supplanted in many immunization programs by vaccines covering more serotypes, such as PCV9 and PCV13, and is no longer widely used in many countries.