Rates of disease caused by the bacterium Streptococcus pneumoniae could be substantially reduced if changes are made to vaccination programmes, according to a study published today.
Researchers from the Wellcome Sanger Institute, Simon Fraser University in Canada, and Imperial College London, have identified how vaccines could be optimised for specific age groups, geographic regions and communities of bacteria by combining genomic data, models of bacterial evolution and predictive modelling.
The study, published in Nature Microbiology, simulated the performance of vaccines over time to assess the risk of vaccine-targeted strains being replaced by other potentially dangerous strains. Researchers identified new vaccine designs that could help reduce overall rates of disease.
Vaccines against pneumococcus have prevented millions of infections, but like many bacteria, S. pneumoniae is difficult to target with vaccines because infection can be caused by different serotypes.
Because there are approximately 100 S. pneumoniae serotypes around the world, vaccine effectiveness varies between countries depending on which serotypes are present.
In this study, the researchers optimised a computer model to approximate the effect of vaccines targeting different serotype combinations.
Analysis of vaccine effectiveness was then carried out on S. pneumoniae genomic data from Massachusetts, USA, and the Maela refugee camp in Thailand, with the researchers developing an efficient method that made it feasible to identify the best-performing designs from the trillions of possibilities.
The team discovered that rates of infant IPD in Maela could be reduced by omitting components from the PCV13 vaccine to keep certain serotypes in place, while in Massachusetts, a vaccine targeting 20 serotypes was found to be more effective than the current PCV13.
They say the results highlight the need for vaccine programmes to be tailored to specific communities of bacteria and to consider vaccination at different ages.
Dr Nicholas Croucher, of the MRC Centre for Global Infectious Disease Analysis, Imperial College London, said: "Our research shows that the best vaccine designs strongly depend on the bacterial strains present in the population, which vary considerably between countries. The best vaccine designs also depend on the age group being vaccinated.
“These ideas will be critical for applying lessons learned from introducing vaccines in high-income countries to combatting the disease where the burden is highest."
The study also found that adult disease rates could be reduced by almost 50% by redesigning adult vaccines to complement those administered to infants.
Professor Caroline Colijn, of Simon Fraser University and the Wellcome Sanger Institute, said: "This approach to optimising vaccines will help to address several problems, such as invasive disease among infants or adults and minimising antibiotic resistance in the post vaccine population. Such an approach also enables public health policy-makers to assess the likely effectiveness of an existing vaccine for a local population based on genomic surveillance data."
Colijn C, Corander J and Croucher NJ. Designing ecologically optimised pneumococcal vaccines using population genomics. Nature Microbiology 3 February 2020; doi: 10.1038/s41564-019-0651-y
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