Infection- plus vaccine-induced immunity led to decline of mpox in Netherlands, data reveal

News brief

Immunity obtained through infections and post-exposure vaccination—not preventive vaccination—was likely the driving force of reduced mpox transmission in the Netherlands in 2022, according to new work from the Dutch National Institute for Public Health and the Environment (RIVM) published late last week in Eurosurveillance. The researchers also say behavior change also likely played a role.

The Netherlands reported its first mpox case on May 20, 2022, at the beginning of a global outbreak, and by December 31, 2023, a total of 1,294 cases had been documented. As in other countries, 94% of cases were among men who have sex with men (MSM), and 99% of cases occurred in males.

The primary preventive vaccination (PPV) program was launched on July 25, 2022, but the researchers showed that cases were already declining by early July among MSM.

Vaccine protection almost 70%

Overall, 29,851 PPV doses were administered from July 25, 2022 to April 30, 2023. The overall vaccine uptake rate was 45.8%, with 35.4% of the target population being fully vaccinated. The effectiveness of preventive vaccination was estimated at 68.2%.

The authors said the PPV program started at the peak of mpox transmission in the Netherlands.

"By the time PPV would be effective, the incidence was already down to [about] five cases per day, making it unlikely that PPV contributed significantly to the decline of the outbreak," the authors said.

The role of behavioural change could unfortunately not be adequately studied with the available data, but based on other studies it should not be ignored.

Infection-acquired immunity in a substantial proportion of those most at risk was the main factor in declining cases, with behavioral changes also likely playing a role, the authors concluded. "The role of behavioural change could unfortunately not be adequately studied with the available data, but based on other studies it should not be ignored," they noted.

PAHO issues dengue alert for Central America, Mexico, Caribbean

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Lisa Schnirring

The Pan American Health Organization (PAHO) urged countries in Central America, Mexico, and the Caribbean to strengthen their efforts to prevent dengue infections, given that those areas are entering their increased transmission season and that countries in South America have reported record activity this year.

In a May 24 epidemiologic alert, PAHO said the Americas region this year has already reported more than 8.1 million dengue cases, a 3.3-fold increase over the same period last year. More than 3,600 deaths have been reported among the cases. The hardest-hit countries include Brazil, Argentina, Paraguay, Peru, Colombia, and Mexico.

In Mexico and some Central America countries, dengue cases are already up between 2.5 and 6 times higher than the same time in 2023. In the Caribbean region, cases are up 5.7-fold from the previous year.

PAHO urged countries to focus on early diagnosis and proper management to prevent severe illness and death. It also urged public health officials to emphasize the importance of eliminating mosquito breeding sites and for people to avoid mosquito bites by wearing insect repellent and clothing to protect the arms and legs.

China reports fatal H5N6 avian flu case

News brief

Lisa Schnirring

China has reported a fatal H5N6 avian flu infection in a 52-year-old woman from Fujian province in the southeastern part of the country.

Hong Kong's Centre for Health Protection (CHP) said the woman's symptoms began on April 13, and she was hospitalized on April 20, where she died on April 30. An investigation found that she had been exposed to backyard poultry before she became ill.

market chickens — *photoncatcher / iStock*

The woman was from Quanzhou, Fujian province's largest city, which has a population of more than 8 million.

China's 90th case in a decade

Highly pathogenic H5N6 is known to circulate in poultry from China and other Asian countries, but so far, China and Laos are the only nations that have reported human cases. Human cases are rare and mostly occur in people who have contact with poultry or poultry environments. The infections are often severe or fatal.

China has now reported 90 H5N6 cases since the first human illness was reported in 2014. The country reported its last case in the middle of January.