'Tailor-made' vaccines needed to reduce infection rates, research shows

Disease rates could be substantially reduced if we changed our approach to vaccine development, a new study suggests.

Researchers from the Wellcome Sanger Institute, Simon Fraser University in Canada and Imperial College London have identified how vaccines could be optimised for specific groups of people, potentially increasing their effectiveness.

The researchers combined genomic data, models of bacterial evolution and predictive modelling to assess the risk of vaccine-targeted strains of Streptococcus pneumoniae being replaced by other potentially dangerous strains.

This predictive modelling approach enabled the researchers to identify how new vaccines could be optimised to treat specific age groups, geographic regions and communities, to help reduce overall rates of disease.

Often found at the back of the nasal cavity, S. pneumoniae is usually harmless, but can migrate to other parts of the body and cause serious bacterial infections, including pneumonia, sepsis and meningitis - known collectively as invasive pneumococcal disease (IPD).

Like many bacteria, S. pneumoniae is difficult to target with vaccines as infection can be caused by different serotypes. Each part of a vaccine usually protects against a single serotype, with the most complex pneumococcal conjugate vaccine (PCV13) targeting 13 serotypes.

And because there are approximately 100 S. pneumoniae serotypes around the world, vaccine effectiveness varies between countries depending on which ones are present.

In this new study, researchers used a computer model to approximate the effect of vaccines targeting different serotype combinations. The teams then carried out an analysis of vaccine effectiveness for S. pneumoniae genomic data from Massachusetts, USA and the Maela refugee camp in Thailand.

S. pneumoniae vaccines are particularly complex due to the range of serotypes. In Maela, for example, the presence of 64 S. pneumoniae serotypes means around 100 trillion vaccine designs are possible, but it would take 19,000 years to simulate them all. By using computer modelling, the researchers were able to develop a more efficient method to identify the best-performing vaccine designs.

The team discovered that rates of infant IPD in Maela could actually be reduced by omitting components from the PCV13 vaccine to keep certain serotypes in place, removing the possibility of their replacement by highly-invasive serotypes. In Massachusetts, a vaccine targeting 20 serotypes was found to be more effective than the current PCV13.

The researchers state their 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.”

More so, the findings of the study coincide with the growing threat of antimicrobial resistance (AMR), as S. pneumoniae infections can be resistanct to multiple antibiotics and have been highlighted as a priority threat by the World Health Organisation.  Indeed, the study showed how vaccines can be designed to reduce the chances of a person’s S. pneumoniae becoming resistant to common medicines.

Professor Jukka Corander, of the University of Oslo, University of Helsinki and the Wellcome Sanger Institute, added: “With the power of the latest DNA sequencing technology we are heading towards a future where large-scale genomic surveillance of major bacterial pathogens is feasible. The approach we describe in this study will play an important role in accelerating future vaccine discovery and design to help reduce rates of disease.”

The study was published in Nature Microbiology.