Published Online: January 26, 2016
Streptococcus pneumoniae (the pneumococcus) is a major cause of child mortality, with an estimated 1 million deaths each year, occurring mostly in the developing world. Protection against the pneumococcus is achieved through vaccination for which there are 2 major types of vaccines available: the pneumococcal conjugate vaccines (PCVs), which are given during infancy and contain up to 13 serotypes, and the pneumococcal polysaccharide vaccine (23vPPV) which contains 23 serotypes. 23vPPV is not given to infants less than 2 years of age due to immaturity of their immune system and so is usually given to high risk older children and adults. In Australia it has been used as a booster for Indigenous children who have received PCV in infancy. The use of 23vPPV in children is controversial owing to reports of impaired immunity produced following vaccination. Although the clinical relevance of this is unknown, any impairment of immunity would leave children at increased susceptibility to pneumococcal disease at an age when their risk of disease is highest.
In a recent paper by Licciardi and colleagues published in The Journal of Allergy and Clinical Immunology (JACI), the long-term impact of 23vPPV given to Fijian children (N=185) at 12 months of age was examined. In a previous paper by the authors, children given 23vPPV as a booster vaccine at 12 months of age were no longer able to respond to a small challenge dose of the vaccine at 18 months of age, while children who did not receive the 12-month 23vPPV dose had good responses. The authors evaluated the long-term effects of this outcome 4-5 years later by undertaking a comprehensive assessment of pneumococcal immunity, nasopharyngeal carriage and hospitalisation history in these children before and after a booster dose with PCV13.
After 5 years, all children produced robust immune responses to PCV13 regardless of whether or not they had received 23vPPV at 12 months of age. No significant differences in any of the immune response parameters measured, including levels and function of pneumococcal-specific antibodies as well as number of memory B cells (important for long-term protection against pneumococcus) were observed between children who had or had not received the 12-month 23vPPV dose. Furthermore, pneumococcal carriage and hospitalisation rates were similar between these groups.
In summary, these findings indicate that the 23vPPV-induced impaired immunity in toddlers does not appear to be sustained among preschool children and does not affect the pneumococcal carriage rate in this age group. However, continued use of 23vPPV in early childhood is not recommended based on the possibility that the observed impaired immunity may be associated with a transient increase in the risk of disease.
The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.