Pneumococcal vaccines.

Streptococcus pneumoniae continues to take a heavy toll on childhood mortality and morbidity across the developing world. An estimated 10.6 million invasive pneumococcal diseases (IPDs) occur every year, with nearly 1 million deaths in children under 5 years of age. Introduction of vaccines in the childhood immunisation programme in developed world has brought down the incidence of the disease considerably. However, childhood immunocompromising illnesses including HIV have increased the risk of IPD several folds. There is also a growing concern on the increasing antibiotic resistance among these invasive strains to penicillin, other beta-lactams and macrolides, making treatment difficult and expensive. It is estimated that about 62% of IPD worldwide is caused by the 10 most common serotypes. Although the ranking of individual pneumococcal serotypes causing serious disease varies among nations, the 7-13 serotypes included in pneumococcal conjugate vaccines (PCVs) may prevent 50%-80% of all paediatric pneumococcal diseases globally. The World Health Organization has recommended the use of PCV-10/13 in the national immunisation programmes (NIPs) of developing countries. Four doses of PCV-13 have been recommended by the US Association of Pediatrics and Centers for Disease Control and Prevention, at intervals of each 2 months for the first 6 months and by the 12 to 15 months after birth. This is expected to reduce the morbidity and mortality associated with IPD and simultaneously decrease colonisation with circulating antibiotic-resistant strains in immunized communities. Nevertheless, continued surveillance of antimicrobial resistance in non-vaccine serotypes is necessary to prevent the resurgence of resistance. Other virulence factors which are not serotype specific also need to be studied to overcome the drawbacks of serotype-specific pneumococcal vaccines. PCV-13 was launched during May 2017 under the NIP of five Indian states with the highest pneumococcal diseases in the country and is expected to be rolled out in the other parts of the country in the coming days.