Pneumococcal Conjugate Vaccine (PCV13) Effective in HIV-negative African Children

The benefit of the pneumococcal conjugate vaccine (PCV13) in African children who are not infected with HIV, including those who were exposed to the infection and malnourished children were recently published in The Lancet Global Health. Pneumococcal disease is caused by a type of bacterium called Streptococcus pneumoniae which has several serotypes or strains. It spreads through secretions of the respiratory tract and causes a lung infection called pneumonia. Though antibiotics are available, development of resistance by the bacteria has reduced the effectiveness of the treatment.

People with reduced immunity including children, older individuals and people with HIV can suffer from complications like middle ear infection, septicemia (blood infection) and meningitis (inflammation of the covering of the brain). These could result in deafness, brain damage and even death. Therefore, the importance of prevention of the infection should not be underestimated.

Two vaccines are available for the prevention of pneumococcal disease – the PCV13 which is used in children as well as in adults, and the PPSV23 (pneumococcal polysaccharide vaccine) which is used in adults and children over two years of age. The older PCV7 which was effective against seven serotypes of the bacteria has been replaced by PCV13 which is effective against thirteen serotypes. PCV13 is usually given in 3 doses, at 6 weeks, 14 weeks at and 9 months of age.

The effectiveness of PCV13 has been proved in countries like the US and UK, but not in vaccine in the low-to-middle income where HIV is highly prevalent and the infection is most likely to cause complications.

In their study, the research team evaluated the effectiveness of PCV13 in the prevention of invasive pneumococcal disease in children with or without HIV in Africa. The study enrolled 726 children of the ages of 16 weeks or older but less than 5 years with invasive pneumonia, with or without HIV. Controls were also enrolled for the groups. They found that:

• Two or more doses of PCV13 had an effectiveness against invasive pneumococcal disease caused by the serotypes present in PCV13 of 85% in children not infected with HIV and 91% in children with HIV
• In children without HIV infection:
• The effectiveness of the vaccine against invasive pneumococcal disease caused by all serotypes was 52%
• The effectiveness was 94% for serotype 19A. The serotype 19A is present in PCV13 but not PCV7.
• The research team did not note negative vaccine effectiveness against non-PCV13 serotypes
• The effectiveness of PCV13 against invasive pneumococcal disease caused by serotypes in the PCV7 vaccine was 87% in children who were exposed to HIV but not infected and 90% in malnourished children not infected with HIV. Malnourished children are particularly prone to invasive pneumococcal disease

The vaccine is also effective in children with HIV; however statistical significance could not be established due to the small number of patients in the group.

Thus, the study re-iterates the importance of continuing the administration of the vaccine in children of the low-to-middle income countries. It must however be remembered that Streptococcus pneumoniae has several serotypes that are not covered by the vaccine and could emerge as important pathogens following widespread use of the vaccine. Therefore, a continued assessment of the efficacy of PCV13 in preventing invasive pneumococcal disease is important, especially in the low-to-middle income countries, where the disease and its complications are highly prevalent.

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References:

1. Cohen C et al. Effectiveness of the 13-valent pneumococcal conjugate vaccine against invasive pneumococcal disease in South African children: a case-control study. DOI: http://dx.doi.org/10.1016/S2214-109X(17)30043-8
2. About Pneumococcal Disease - (https://www.cdc.gov/pneumococcal/about/)

Source-Medindia