A comprehensive review of data covering billions of administered doses of mRNA vaccines has concluded that the technology remains both safe and highly effective in preventing infectious diseases, with researchers urging governments and health organisations to focus on expanding global access.

The review, published in The Lancet, examined evidence gathered since mRNA vaccines were first deployed on a large scale during the COVID-19 pandemic. Researchers found that the vaccines continue to provide strong protection against severe illness while serious side effects remain uncommon.

Unlike conventional vaccines, mRNA vaccines work by delivering genetic instructions that enable the body’s cells to produce a harmless viral protein. This process trains the immune system to recognise and respond to future infections without altering a person’s DNA.

According to the review, mRNA vaccines were 87% effective in preventing confirmed SARS-CoV-2 infections within 14 to 42 days after vaccination. The vaccines also demonstrated 93% effectiveness in preventing hospital admissions and 94% effectiveness in preventing deaths related to COVID-19 during the same period.

Researchers noted that immunity declines over time, but booster doses restore a significant portion of the lost protection.

The review also assessed vaccine safety across billions of administered doses. It found that serious adverse events, including myocarditis, pericarditis and anaphylaxis, occurred very rarely. Most reported reactions, such as pain at the injection site, fatigue and fever, were mild to moderate and typically resolved within a few days.

“Across billions of administered doses, serious adverse events have been rare, well characterised, and consistently outweighed by the substantial protection conferred against severe disease, hospitalisation, and death,” the researchers wrote.

The review concluded that the vaccines have proven effective across a broad range of populations, including children, older adults, pregnant women and people with weakened immune systems.

Researchers also highlighted the growing potential of mRNA technology beyond infectious diseases. They said ongoing research could lead to personalised cancer vaccines designed to match an individual patient’s tumour characteristics, opening new possibilities for targeted treatment.

Co-author Manish Sadarangani of the University of British Columbia and BC Children’s Hospital Research Institute said mRNA vaccines have already changed how the world responds to emerging infectious diseases and could continue to play an important role in preventive medicine and cancer care.

The review also noted that improvements in vaccine storage, including higher-temperature storage methods and freeze-drying technologies, could simplify transportation, reduce waste and improve access in remote regions.

Despite these advances, the researchers stressed that manufacturing capacity and equitable distribution remain major challenges. They called for greater investment in local production, technology transfer and stronger regulatory systems, particularly in low- and middle-income countries.

Co-author Robin Shattock of Imperial College London said expanding manufacturing networks and strengthening regional production capabilities would shorten supply chains, lower costs and help ensure countries have faster access to vaccines during future global health emergencies.

Record-breaking summer heatwaves and rising sea temperatures are creating favourable conditions for the spread of Vibrio bacteria in European coastal waters, prompting health experts to advise caution for swimmers and seafood consumers, particularly in areas where fresh and salt water meet.

Vibrio is a naturally occurring group of bacteria that thrives in warm, moderately salty coastal waters. While most strains are harmless, some can cause illnesses collectively known as vibriosis, which may affect people through contact with contaminated water or by eating raw or undercooked seafood.

Health authorities say infections remain relatively uncommon in Europe, but the number of reported cases has increased during particularly warm summers, raising concerns that climate change could expand the bacteria’s range.

According to the European Centre for Disease Prevention and Control (ECDC), the Baltic Sea, the transition zone between the Baltic and North Seas, the Black Sea and coastal regions influenced by large rivers are among the areas where Vibrio is most commonly found.

The bacteria can enter the body through open cuts or wounds while swimming in contaminated water. Infections may also occur after consuming contaminated shellfish, especially raw oysters.

Symptoms vary depending on how the infection is acquired. Water-related infections may cause ear infections or skin irritation, including redness, swelling and pain around wounds. In severe cases, untreated infections can spread into the bloodstream, leading to sepsis, tissue damage and, in rare situations, limb amputations.

One of the most dangerous strains, Vibrio vulnificus, is sometimes referred to as a “flesh-eating” bacterium because of its ability to rapidly destroy tissue. Serious illness remains rare but is more likely among people with weakened immune systems, chronic liver disease or other underlying health conditions.

The ECDC said Europe recorded a significant rise in infections during the exceptionally warm summer of 2018, when 445 cases were reported. That figure was more than three times the annual median of 126 cases recorded between 2014 and 2017.

Scientists believe warmer seas and more frequent heatwaves are contributing to the bacterium’s spread. The European Food Safety Authority (EFSA) has also warned that increasing ocean temperatures are expected to raise Vibrio levels in seafood worldwide.

Health experts recommend avoiding raw or undercooked shellfish and ensuring seafood is cooked thoroughly before consumption. People with cuts, wounds or recent piercings are also advised to avoid swimming in brackish or salt water until the skin has fully healed.

To help monitor potential risks, the ECDC operates an interactive forecasting system that tracks Vibrio conditions across Europe and provides daily updates with five-day predictions. Officials say the tool can help residents and tourists make informed decisions during periods of unusually warm coastal waters.