Evaluating Vaccine Responses in Healthy Infants Receiving Their Routine Primary Immunisation According to the Accelerated United Kingdom Schedule at 2, 3 and 4 Months (P13UK)

Streptococcus pneumoniae is a major cause of serious bacterial infections, particularly among young children. Over 30 different types of the pneumococcus germ can cause invasive disease, but 7 types (namely serotypes 4, 6B, 9V, 14, 18C, 19F and 23F) are responsible for around 75% of cases in young children. A pneumococcal conjugate vaccine against these 7 serotypes (PCV7; Prevenar ®, Wyeth Vaccines) was introduced into the UK national immunisation programme in September 2006 and has resulted in a rapid reduction in pneumococcal disease caused by the 7 serotypes among both vaccinated children and older unvaccinated children and adults through herd immunity. By 2009, over half of all invasive pneumococcal cases in young children were caused by six other pneumococcal serotypes (1, 3, 5, 6A, 7F and 19A) that are included in a newly licensed 13 valent pneumococcal vaccine (PCV13; Prevenar 13®, Wyeth Vaccines). In April 2010, PCV13 replaced PCV7 in the UK immunisation programme with the aim of further reducing cases of invasive pneumococcal disease. The antibody responses induced by the 7 serotypes in both PCV13 and PCV7 have been shown to be comparable, but the protection offered by the additional 6 serotypes in PCV13 merits further study. Also, it is possible that the use of PCV13 instead of PCV7 may interfere with immune responses to other vaccines, such as Haemophilus influenzae serotype b (Hib), which are given to infants at the same time as PCV13. The proposed study will aim to collect one blood sample from infants after they receive their routine vaccinations at 2, 3 and 4 months in order to their measure immune responses to routine vaccines. The investigators hope that their results will help us better understand the added protection offered by the 13valent pneumococcal vaccine and ensure that children are adequately protected by the other vaccines they receive.