Research insights: the latest updates from clinical papers

Covid vaccines not linked to sudden death in young adults

Covid-19 vaccines do not increase the risk of sudden cardiac death in apparently healthy younger adults, a Canadian study has found.

The study, which was published in PLOS Medicine on 19 March, examined data from nearly 5,000 people who were alive as of 1 April 2021 and considered to have died from sudden cardiac death by 30 June 2023.

To rule out anyone who might not otherwise be considered healthy, the researchers excluded people aged over 50 years and those with documented cardiovascular disease, mental illness, or diseases that would predispose them to adverse outcomes from Covid-19. Furthermore, they matched each case to five living controls on age, sex, region, and neighbourhood income – yielding 24,030 controls.

Not only was vaccination against Covid-19 not associated with increased risk of sudden cardiac death among younger adults, the researchers also found that vaccinated people had a roughly 43% lower risk of sudden cardiac death compared with those who were unvaccinated.

According to the authors, these findings not only support the continued use of Covid-19 vaccines and refute claims that they cause sudden cardiac death in young adults but also align with the results of previous studies from the UK and USA.

Flu vaccine cuts children’s hospitalisation risk by up to 60%

The influenza vaccine reduced the risk of children being admitted to hospital by as much as 60% during one flu season, according to a new study.

Published in Pediatrics on 6 April, the study examined nearly 20,000 children aged between six months and 17 years across seven hospitals in the USA over three flu seasons (2021-2024). It found that vaccine effectiveness ranged from 34% in 2021-2022 to 60% in 2023-2024.

Furthermore, the researchers found that the vaccine protected against some flu strains more than others. It was 69% effective against influenza B, 53% effective against influenza A/H1N1 and 43% effective against influenza A/H3N2.

Importantly, the researchers noted that vaccination uptake among eligible children was low, with only half or fewer receiving the influenza vaccine each season. They recommend improving paediatric vaccination uptake in order to prevent additional influenza-associated hospitalisations and outpatient visits.

Vapes likely increase cancer risk

Nicotine-based vapes are likely to increase the risk of cancers of the lung and oral cavity, according to a recent review.

The study, published in Carcinogenesis on 30 March, analysed evidence from animal studies, human case reports, and laboratory research published between 2017 and 2025 to assess whether vaping may be linked to cancer.

There is currently no long-term evidence showing that vaping directly causes cancer, partly because e-cigarettes have only been widely used since the early 2000s and cancer can take many years to develop. Instead, the review examined whether vaping is associated with biological changes in the body that are known to contribute to cancer.

The researchers identified several potentially carcinogenic compounds in e-cigarette aerosols, including volatile organic chemicals, nicotine-derived substances, flavouring agents, and metals released from heating coils. They also found evidence of early warning signs linked to cancer risk, such as DNA damage, oxidative stress, inflammation, and changes in gene regulation in oral and lung tissues.

Additionally, the animal studies included in the review reported lung tumours in mice exposed to e-cigarette vapour, while laboratory studies showed cellular damage and disruption of biological pathways associated with cancer.

Overall, the review concludes that nicotine-based e-cigarettes are likely to be carcinogenic to humans – though the exact level of risk remains uncertain.

New antibiotics leave drug-resistant infection mortality unchanged

Despite the approval of nine next-generation antibiotics to treat antimicrobial-resistant Gram-negative infections, mortality among patients with these infections remains unchanged, a new study from the USA has found.

Published on 25 March in The Lancet Infectious Diseases, this retrospective study analysed data from 5,065 patients from 262 hospitals with confirmed difficult-to-treat resistant infections caused by Enterobacterales, Pseudomonas aeruginosa, or Acinetobacter baumannii between January 2016 and August 2023.

Although the proportion of hospitals using at least one newer antibiotic rose from 12% to 63% over the study period, 84% of patients were still receiving initial therapy with an antibiotic with no proven activity against their pathogen – known as in-vitro discordant therapy – as recently as 2023.

Notably, no statistically significant change in mortality was observed across the study period for any of the three pathogens. Furthermore, mortality did not differ between patients who received a newer antibiotic and those who received a traditional antibiotic only, nor did researchers observe any significant difference between those who received in-vitro discordant compared with concordant initial therapy.

The authors suggest that investment in rapid diagnostic platforms – to enable earlier, targeted treatment – alongside clinical trials specifically enrolling patients with difficult-to-treat resistant infections, and exploration of non-antimicrobial therapies, may be needed to meaningfully reduce mortality in this patient group.

A quarter of pregnant women have anaemia

The rates of women experiencing anaemia during pregnancy rise from one-in-20 at the start of prenatal care to one-in-four later in the gestation period, a US study has found.

Published in Obstetrics & Gynecology on 26 March, this research letter analysed data from a claims database of commercially-insured patients from 2018 to 2023 that included 65,528 pregnancies.

The study defined anaemia as a haemoglobin level of less than 11 g/dL or a haematocrit level of less than 33% in the first and third trimesters, and as a haemoglobin level of less than 10.5 g/dL or a haematocrit level of less than 32% in the second trimester.

The researchers found that the overall prevalence of anaemia during pregnancy was 25.6% in this cohort, which was more than double previous estimates. Moreover, the prevalence of anaemia was 4.3% at prenatal care initiation and 24.5% at mid-pregnancy – reflecting the rapid depletion of iron stores associated with advancing gestational age.

The authors emphasise that these findings underscore the need for proactive screening and treatment to prevent the development of anaemia in pregnant women.

Hydration ineffective at preventing kidney stones 

Increased fluid intake did not reduce the occurrence of kidney stones but ‘modestly’ increased urine volume, according to a new study from the USA.

The randomised clinical trial was published on 19 March in The Lancet and comprised of 1,658 people aged 12 years and older with a history of kidney stones. Participants were randomised one-to-one to either a behavioural intervention group designed to promote fluid intake or to a control group.

Participants in the intervention group received a Bluetooth-enabled bottle that tracked how much water they drank and were offered financial incentives, coaching, and encouragement to help them reach a personalised hydration goal. Meanwhile, those in the control group received care in line with current guidelines for recurrent urinary stones.

Rather than just measuring fluid intake and urine output, the researchers focused on the most clinically relevant outcome – symptomatic kidney stone recurrence – to assess whether the intervention was effective.

The researchers found that there was no meaningful difference between the groups in terms of stone growth of at least 2mm or in the formation of new stones from the start of the study to the final scan. However, while 24-hour urine volume increased in both groups it was higher in the intervention group.

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A version of this article was first published on our sister title, The Pharmacist.