No changes in mortality rates from life-threatening infections over the last decades

Despite incidences of invasive pneumococcal infections having subsided considerably since vaccinations were introduced in 2011, mortality rates for patients who get these types of infections haven’t changed over the decades, according to a new long-term study conducted by scientists at the University of Iceland and Landspitali – University Hospital.

The results were published in the prestigious science journal Clinical Infectious Diseases. These are the most serious cases of pneumococcal infections that are diagnosed, and are most often related to blood poisoning, pneumonia, or meningitis, and involve high mortality rates. The article was first published online, but will be published in its final draft later this year.

“Streptococcus pneumoniae is a major global cause of pneumonia, and the infections it causes are among the most serious we encounter. The data show that mortality rates, both short- and long-term, have changed little over the decades. Along with huge progress in almost every field of medicine, we thought these patients had fared better through the years,” says Hörður Tryggvi Bragason, the main author of the article. He worked on the project partly as a med student at the University of Iceland under the guidance of Magnús Gottfreðsson, professor of medicine at UI, and chief physician in infectious diseases at the Landspitali.

Hörður Tryggvi has graduated and is now a resident doctor in internal medicine at the Landspitali, however, he has stood out before for exceptional academic performance. Hörður completed his medical degree with distinction and graduated at the top of his class from Menntaskólinn í Reykjavík (Reykjavík College) in 2028. Magnús Gottfreðsson is the senior author of the article.

One of the most extensive long-term research project of its kind

The research project is unique in terms of its scope and duration. It spans a 45-year period and is based on nationwide data covering all cases with positive blood or cerebrospinal fluid cultures, ensuring accurate analysis and registration. Such a comprehensive approach is rare globally and enables analysis of long-term changes in disease frequency, the spread of different serotypes, and the evolution of mortality rates.

“As far as I know, no one has done any research on this subject over such an extended period of time. Our data covers the entire country and spans 45 years, so we saw a unique opportunity to examine something that hadn’t been researched fully before,” Hörður says.

Fewer incidences with the introduction of vaccines

The research also shows clearly that the frequency of infections in Iceland has decreased considerably since pneumococcal vaccination began in 2011. The vaccination has had a significant impact on the spread of serious infections in the community, among both children and adults, including on herd immunity. The frequency of infections peaked between 1995 and 2004, but has dropped both sharply and significantly since 2011. The reduction was greatest among children, but a substantial decrease was also observed among adults, underlining the importance of the indirect effects of vaccination on the population as a whole.

Increased mortality throughout life among survivors

In the longer term, it has also emerged that people who survive an invasive pneumococcal infection live with a substantially increased risk of mortality compared with the general population. Even when those who die from the sudden infection are excluded, it has been shown that survivors’ long-term mortality is approximately 2.6 times higher than in the general population. This indicates that the disease has permanent health effects, in addition to many patients fighting underlying chronic diseases.

“In recent years, it has become clear that some infections we thought were restricted to a short period of time, i.e. the period of time when patients experience acute symptoms, aren’t that simple. Rather, they seem capable of inducing long-term changes in health and well-being, which, in the case of invasive pneumococcal infections, are closely associated with increased mortality rates, long after the infection has been treated and thought to be over. This needs to be examined further,” says Magnús Gottfreðsson, professor in the Faculty of Medicine at UI and one of the authors.

The research also shows that, despite successful preventive measures, there is an urgent need for further action to reduce mortality rates during the disease’s acute phase, for example, through more systematic diagnosis, faster treatment, and better support for more vulnerable patient groups.

Important clues for policy development and the healthcare system

The findings of this highly compelling research project have far-reaching implications for public health and policymaking. They further reinforce the importance of childhood vaccination, not only for children themselves but for society as a whole. The results also demonstrate that success in prevention can fundamentally alter the epidemiology of severe infectious diseases at the national level.

At the same time, the research highlights that reducing case numbers alone is insufficient. To improve patient outcomes, authorities must adopt a more holistic approach that encompasses prevention, acute care, and long-term follow-up for survivors of severe infections.

Both Hörður and Magnús note that it is striking, yet unsettling, to have confirmation that mortality during the acute phase of infection has remained unchanged over recent decades. In the management of most other life-threatening diseases, they have observed substantial advances in diagnosis and treatment, while that progress clearly doesn‘t apply to these severe infections, and addressing this should be a priority.

The study represents an important contribution by Icelandic scientists to the international discourse on pneumococcal disease and illustrates how the interplay of high-quality registries, long-term research, and robust vaccination programmes can yield tangible benefits for society. It also underscores the importance of collaboration between the University of Iceland and Landspitali, and the vital roles both institutions play in generating knowledge with real impact on people’s health, nationally and internationally.