Antibiotics for sore throats have hardly any preventive effect against serious streptococcal infections in the population, according to a study from the University of Gothenburg. Instead, healthcare needs to quickly recognize warning signs of a serious infection.
Group A streptococcus (GAS) is a common bacterium that can cause invasive GAS infection (iGAS) if the bacteria enter, for example, the blood or lungs. The condition is potentially life-threatening and relatively uncommon, but its incidence has increased in recent years in several countries.
Since uncomplicated sore throats can sometimes develop into iGAS, or infect others in the community, early antibiotic treatment is often debated as part of preventive measures.
However, the researchers behind the current study, published in the International Journal of Infectious Diseases, show that prescribing antibiotics for uncomplicated acute sore throats, with the aim of preventing iGAS, has very limited effect at the population level.
"The intention to prevent iGAS infections should no longer be used as an argument for treating common throat infections with antibiotics, that strategy is greatly overrated", says Ronny Gunnarsson, lead author of the study, Family Physician and Professor Emeritus at the University of Gothenburg.
Minimal preventive effect
By combining scientific evidence with epidemiological data for the entire Swedish population in 2024, the researchers have calculated how different strategies affect the incidence of iGAS.
The results show that even in an extreme scenario - where all patients seeking care for a sore throat are tested and treated if they carry the bacteria - at most 6.7 percent of iGAS cases could be prevented in children and 2.8 percent in adults.
If current Swedish guidelines are followed instead, where testing is only done if the patient meets three to four specific symptoms according to the Centor criteria, the preventive effect is a maximum of 1.6 percent in children and 1.2 percent in adults.
The proportion of iGAS cases that can actually be prevented with antibiotics is much smaller than one might think. Our calculations show that throat swabs must be taken from between 45,000 and 110,000 patients, and up to 110,000 antibiotic prescriptions must be written, just to prevent a single case of iGAS."
Ronny Gunnarsson, University of Gothenburg
Contagious before the healthcare visit
The researchers point to several reasons why antibiotics are ineffective against iGAS at the population level. Most people who get a sore throat never contact a health care center. Those who do usually seek care on the third day of illness or later, when they have already passed their most contagious period.
In addition, 15-25 percent of iGAS patients are infected by asymptomatic carriers, i.e. people who feel completely healthy and who therefore should not have antibiotics. The study concludes that a lowered threshold for testing and treating sore throats would lead to major negative consequences for the primary care.
"Broadening the criteria for sampling and antibiotic treatment would mean an enormous burden for primary care and crowd out other patient groups, not to mention the risk of side effects from antibiotics", says Ronny Gunnarsson, and continues: "Instead of prescribing antibiotics for uncomplicated sore throats, healthcare should focus on quickly recognizing early warning signs of serious infection, and in the long term await a safe and effective vaccine against streptococci."
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