‘We don’t understand what’s going on’
Experts stumped, but new vaccines offer hope as mosquito-borne illnesses resurge in Caribbean
Published:Friday | May 2, 2025 | 12:17 AMMickalia Kington/Gleaner Writer
The resurgence of mosquito-borne illnesses like dengue, chikungunya, and Zika remains a pressing concern across Latin America and the Caribbean. In response, top virologists gathered yesterday at The University of the West Indies (UWI) Mona Campus for a workshop hosted in partnership with the Global Virus Network (GVN).
Dr Scott Weaver, director at the University of Texas Medical Branch’s Institute of Human Infections and Immunity, addressed health professionals and researchers, offering insights into recent trends and vaccine developments.
Weaver linked the spike in dengue cases in 2024 to multiple factors.
“Most people attribute, at least partly, to climate change, urbanisation, the usual factors associated with emergence of these arboviruses,” he said. “I don’t think climate or urbanisation explains all of this … . We really just don’t understand what’s going on here.”
He pointed to an unexpected dip in dengue cases around 2017–2018 possibly due to Zika virus exposure.
“We think that was cross-protective immunity from Zika, but it only lasted a couple of years,” he said, also noting that both viruses are transmitted by the Aedes aegypti mosquito.
Weaver, who has worked on vaccine development and advised on several virus-related panels, provided a critical look at dengue vaccines.
“The first vaccine … produced by Sanofi … turned out to enhance disease when native people were vaccinated, and then subsequently, they were infected by dengue virus,” he said. “This vaccine has virtually disappeared from use.”
A newer option developed by Takeda showed some promise.
“The dengue two part of the vaccine is dominant … . The other three serotypes don’t respond with as robust immunity and, therefore, protection isn’t very strong against all the serotypes. But so far, there’s no major problem with enhancement,” he explained.
However, he was more hopeful about a vaccine developed at the National Institutes of Health (NIH) and licensed to the Butantan Institute in Brazil.
“This one … appears to be truly quadrivalent in the immune response. Antibodies, including neutralising antibodies, are developed in all four serotypes,” he said. “I expect it will be licensed within the next year … and I think it’s going to be a real game changer for dengue.”
‘Big economic impact’
Turning to chikungunya, Weaver emphasised its severity.
“The majority of cases are symptomatic, and a lot of patients develop very severe and often chronic arthralgia,” he said. “So it has a big economic impact … . This was shown here in Jamaica as well as anywhere else.”
He explained how chikungunya’s debilitating effects reduce its spread in larger countries. “We think chikungunya just spreads much less efficiently… because it puts people in bed or often in the hospital,” he said. “Jamaica has a more concentrated population, … so gradual spread can work more efficiently.”
Weaver traced the virus’s arrival in the Americas to two 2013-2014 introductions from Asia and Africa. The East/Central/South African (ECSA) strain has since become dominant.
Weaver traced its arrival in the Americas to two introductions, one from Asia in 2013 and another from Africa in 2014. “This strain seems to be taking over,” he said of the East/Central/South African lineage.
On vaccines, Weaver highlighted Valneva’s IXCHIQ, a live attenuated vaccine licensed in Brazil that offers strong single-dose protection – though not ideal for pregnant women or immunocompromised individuals. He also praised Bavarian Nordic’s Vimkunya, a virus-like particle vaccine recently approved by the US Food and Drug Administration.
“It contains no genetic material … and it’s giving very robust and long-lived immunity after a single dose,” Weaver said. “It’s going to be better for travellers, … and good in endemic areas if this immunity turns out to be very long-lived.”
He also flagged a re-emerging threat: the Western equine encephalitis virus (WEEV).
“This is a virus that we didn’t pay much attention to for a long time,” he said. “But it’s very serious in both people and horses. Up to 10 per cent have respiratory failure. Case fatality overall about four per cent.”
Weaver urged sustained vigilance and fair vaccine access.
“We have the science. Now it’s about infrastructure, education, and delivery,” he said.
The workshop took place at UWI Mona’s Faculty of Medical Sciences, hosted by the GVN, which is a coalition of top virologists from more than 29 countries focused on viral- disease prevention. Jamaica joined the network in 2019, positioning itself as a regional hub for research and response.