Infectious Disease Clinical Trials Update: Week 19, 2026

Published May 8, 2026 — 5 trials covered

By Victor Lafforgue, Founder of TrialsAlert. Blog posts are AI-drafted from ClinicalTrials.gov source data and reviewed by the editorial team. See our editorial policy for details.

Oral Islatravir (MK-8591) Once-Monthly as Preexposure Prophylaxis (PrEP) in Men and Transgender Women Who Are at High Risk for HIV-1 Infection (MK-8591-024)

This Phase 3 trial examined a new way to prevent HIV-1 infection using a once-monthly oral pill called Islatravir. The study included nearly 500 men and transgender women at high risk of HIV infection from multiple countries. If this treatment becomes available, it could simplify prevention by reducing the need to take daily medication, making it easier for people to stay protected.

A Study of mRNA-1283 Injection Compared With mRNA-1273 Injection in Participants ≥12 Years of Age to Prevent COVID-19

This large Phase 3 study tested a new COVID-19 vaccine called mRNA-1283 against the existing mRNA-1273 vaccine in people aged 12 and older. With over 13,000 participants, the trial aimed to find out if the new vaccine could offer better immune protection or improved safety. The results could lead to new vaccine options that help protect more people from COVID-19 with potentially fewer side effects or easier use.

A Study to Evaluate the Safety and Immunogenicity of COVID-19 Vaccine and Influenza Combination Vaccine

This Phase 3 trial is exploring a combined vaccine that protects adults aged 65 and older against both COVID-19 and influenza with a single shot. The study is still ongoing but aims to provide a simpler way to protect against two serious respiratory illnesses at once. If successful, this approach could make it easier for older adults to stay up to date on vaccinations and reduce the burden of multiple injections.

Study to Evaluate the Safety and Efficacy of Emtricitabine and Tenofovir Alafenamide (F/TAF) Fixed-Dose Combination Once Daily for Pre-Exposure Prophylaxis in Men and Transgender Women Who Have Sex With Men and Are At Risk of HIV-1 Infection

This large Phase 3 trial tested a daily pill combining two medications, emtricitabine and tenofovir alafenamide, to prevent HIV-1 infection in men and transgender women at risk. With over 5,000 participants, the study looked at how safe and effective this prevention method is. The results may offer a safer or more convenient daily option to help people stay protected from HIV.

Safety Study of a Vaccine to Help Protect Against Lyme Disease in Healthy Children

This Phase 3 study tested the safety of a new vaccine called VLA15 in over 3,500 healthy children aged 5 to 17 across the United States. Lyme disease can cause serious health problems if not prevented, and this vaccine aims to reduce the risk of infection in children. The available results may lead to a new way to protect children from Lyme disease, especially in areas where the infection is common.

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