On the Caribbean islands, RSV follows a different pattern than in the Netherlands: babies there mainly fall ill between June and December, while in the Netherlands the virus peaks during the European autumn and winter. As a result, the Dutch timing for RSV prophylaxis does not align well with the local situation. This is evident from research conducted by Radboudumc in collaboration with Caribbean hospitals and laboratories.
RSV is a common and contagious virus that causes respiratory infections. Most people experience only mild cold-like symptoms, but in babies the illness can be much more severe, with symptoms such as fever, breathing difficulties, or pneumonia. In some cases, hospitalization is necessary.
To better protect babies, the Netherlands introduced RSV prophylaxis in the autumn of 2025. This prophylaxis protects an infant for about six months. And with success: since its introduction, 75% fewer babies have been admitted to intensive care due to the virus.
In the Netherlands, RSV circulates mainly in autumn and winter. Babies therefore receive the prophylaxis just before or during these seasons. Those born between October and March receive the prophylaxis within two weeks after birth. Babies born outside this period receive the protection in September or October.
Different seasons
In the Caribbean part of the Kingdom, Dutch prevention guidelines are often adopted one-to-one. Together with colleagues, pediatrician, infectious disease specialist, and immunologist Lilly Verhagen from Radboudumc Amalia Children's Hospital wondered whether this approach truly fits the local context: ‘Infections are seasonal. On a tropical island, you don’t have autumn and winter, but a rainy and a dry season.’ Therefore, the researchers examined when RSV peaks on the six Caribbean islands: Curaçao, Aruba, Sint Maarten, Bonaire, Sint Eustatius, and Saba.
Incorrect timing
The study shows that RSV begins to circulate in the Caribbean islands while it is still midsummer in the Netherlands. The virus is most active there between June and December, a period that coincides with the rainy season. During these months, people tend to spend more time indoors and near one another, which may facilitate viral transmission.
The Dutch timing of RSV prophylaxis is therefore not suitable for the Caribbean islands. If a baby receives the prophylaxis in September or October, the child will be protected at the end of the year, but by the time RSV begins to rise again in June, the prophylaxis has largely disappeared from the body.
Adjusting policy
‘An adjustment of the Dutch guideline is therefore necessary,’ says Radjin Steingrover, medical microbiologist on Bonaire and Sint Maarten. According to Verhagen, the prophylaxis is best administered on the Caribbean islands just before the rainy season. ‘This way, we can better protect babies on the islands.’
On Bonaire, Sint Eustatius and Saba, the RIVM is responsible for the prevention guidelines, as these islands are special municipalities of the Netherlands. Babies born there are therefore, just like in the European Netherlands, eligible for RSV prophylaxis. In response to the new research findings, the RIVM is currently assessing whether the timing should be adjusted.
On Curaçao, Aruba, and Sint Maarten, there is currently no RSV prevention in place. These islands are autonomous countries within the Kingdom and are responsible for their own health policies. The researchers will therefore work with local partners to explore how RSV prevention fits within the local context. Verhagen explains: ‘Over the coming year, we will first identify which information is still needed to make well‑informed decisions about RSV prevention on Curaçao, Aruba, and Sint Maarten.’
The research was carried out with local investigators to ensure that island-specific knowledge and healthcare practices were well integrated. More information about the study and the project team can be found on this page. To facilitate discussions about RSV prevention on Curaçao, Aruba, and Sint Maarten in the coming year, the researchers have received follow‑up funding from ZonMw.
About the publication
This research was published in International Journal of Infectious Diseases: Seasonal Dynamics of Influenza and RSV in the Caribbean: A Call for Regionally Tailored Preventive Measures. Charlene Maria, Jayant Kalpoe, Angelino Tromp, […], Peter Klein Klouwenberg, Radjinkoemar Steingrover, Lilly Verhagen. DOI: 10.1016/j.ijid.2026.108498
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