As the threat presented by antimicrobial resistance (AMR) grows globally, the pressure is mounting on the vaccine community to continue contributing to the “toolkit” against AMR. A recent study in eBioMedicine suggests that an effective vaccine against group A Streptococcus (Strep A) could “avert 2.8 million courses of antibiotics” for sore throat treatment in children. This would increase to an “estimated 7.5 million” courses averted if an effective vaccination programme “also reduced precautionary prescribing”.
Strep A and AMR
The authors state that infection by Streptococcus pyogenes, also known as group A Streptococcus or Strep A, is the “most common bacterial case of sore throat”; more than 600 million cases are identified each year worldwide. These infections can cause “severe clinical sequelae” like streptococcal toxic shock syndrome, sepsis, or acute post-streptococcal glomerulonephritis.
Although accurate diagnosis and treatment of Strep A sore throat is “known” to reduce the risk of developing acute rheumatic fever (ARF) and may reduce the risk of other sequelae, “most sore throats are caused by viral infections”, where antibiotics are “ineffective”.
“Difficulties in clinically discriminating between pharyngitis due to Strep A and other pathogens, along with the time and cost associated with performing and processing a diagnostic test, means that many patients are prescribed antibiotics either without testing or before the test result is known.”
Furthermore, in low-resource settings tests are not always readily available, practical, or affordable. Therefore, there is cause for concern that the frequency of antibiotic prescriptions exceeds the necessary number.
“Inappropriate and excessive antibiotic consumption is a major contributor to AMR.”
AMR “reduces antibiotic effectiveness, worsens patient outcomes, and increases treatment costs” with a particular burden borne in lower-resource settings. The study suggests that immunisation with a future Strep A vaccine could prevent necessary prescription of antibiotics for sore throat by preventing Strep A infection and will “likely reduce unnecessary prescription”. Therefore, the development of a vaccine is a “global priority”.
How important would a vaccine be?
The authors believe that understanding the “full scope of antibiotic consumption” for sore throat is “a key part of understanding the potential value” of a vaccination programme. The study sought to:
- Estimate the mean rate and total number of antibiotic courses prescribed to treat sore throat
- Estimate the proportion of prescriptions for sore throat that is attributable to treatment of sore throat caused by Strep A
- Summarise the distribution of antibiotic classes prescribed for sore throat
- Explore the potential reduction in antibiotic prescribing for sore throat due to implementation of prospective Strep A vaccines
The team reviewed and analysed articles published between January 2000 and February 2022 with reference to antibiotic prescribing or consumption, sore throat, pharyngitis, or tonsillitis. They then calculated the estimated reduction in antibiotic prescribing due to the introduction of Strep A vaccines by combining these analyses with assumptions for the effectiveness, duration of protection, and coverage of a vaccine.
From 101 studies across 38 countries the mean prescribing rate for sore throat was “approximately 5 courses per 100 population per year”, accounting for “approximately 5% of all antibiotic consumption”.
“Based on 2020 population estimates for countries with empiric prescribing rates, antibiotic consumption for sore throat was estimated to exceed 37 million courses annually, of which half could be attributable to treatment for Strep A.”
The study suggests that a vaccine that reduces infection rates by 80%, with 80% coverage and a 10-year duration of protection, could avert over 2.7 million courses of antibiotics in 5 to 14-year-olds. A key finding of the study was a lack of published research from low- and middle-income countries, where Strep A disease and complications are “much higher”.
“Understanding sore throat-based antimicrobial use in these countries is critical and may be a major driver of AMR. Equally, the impact of a Strep A vaccine may be even more dramatic in such settings.”
The paper recognises that there is “little empirical data” to estimate the consumption of antibiotics due to sore throat, nor the proportion that is attributable to Strep A infection. These data are “crucial” to understanding the effects of Strep A vaccination, beyond a direct reduction in infections, the “economic and societal value”.