A lack of willing participants has forced a delay in the release of an important national population health survey expected to shed new light on food allergies.

The 2025-2026 cycle of the National Health and Nutrition Examination Survey (NHANES) will be extended to include data from 2027, according to a CDC spokesperson, who said the results would be published in 2028.

“We are currently planning the extra year, pending Ethics Review Board and Office of Management and Budget approval, to assure that we have enough participants to make nationally representative estimates,” Paul Prince, CDC spokesman, told Medscape Medical News. “The reasons for nonparticipation are likely multifactorial, and we cannot be certain that it is any single factor.”

Prince added that the CDC hopes to “reach the same amount of data in 3 years that we previously collected in a 2-year cycle.”

“It sounds like things are a little off-track,” Corinne Keet, MD, PhD, professor of pediatrics at The University of North Carolina at Chapel Hill, told Medscape Medical News in an interview. “Normally it just goes from one cycle to the next, every 2 years, without a pause.”

Keet, who is an allergy and immunology specialist, said that the NHANES, because it is a thorough, nationally representative survey, is an important tool not just for understanding health behaviors but also for tracking health trends. On average, Keet said, there are 10,000 respondents to the survey, half of them children.

“It’s one of the things used for making public health policy,” she said, adding that she and her colleagues have also used the data in their research into food allergies.

To that end, Prince confirmed that the current NHANES cycle is focused on improving understanding of allergies overall.

“For this current cycle, three NIH Institutes collaborated with the National Center for Health Statistics to include respiratory health and allergy content including questions, allergy testing, and lung function testing. Allergy questions and testing were last included in the 2005-2006 cycle and lung function in the 2007-2012 cycles,” Prince noted.

Clinical data such as blood draws and spirometry, when combined with self-reported food intake data, should help to clarify associations between self-reported allergy and respiratory health conditions, allergic sensitivity, and lung function, according to Prince.

This cycle will also include data on the alpha-gal syndrome, ie, allergy to animal products such as meat and dairy that begins with a tick bite, according to Prince. Other food allergy assays, he said, will be used for the nine foods already identified by public health officials as allergens: milk, eggs, tree nuts, soybeans, wheat, peanuts, sesame, fish, and shellfish.

“I’m glad to hear it’s still happening,” Keet said. “NHANES is an amazing amount of work because of the level of data collection,” Keet said. “The questionnaire is super long, they do all these biosamples, [and] they do all these exams. It’s really a lot of dedication from the people who are doing the sample collections and then those who are analyzing everything.”

Keet disclosed holding a noncommercial patent for a sublingual form of immunotherapy and receiving grant, research, and clinical trial support from Genentech, the National Institute of Allergy and Infectious Disease, and the National Institute of Environmental Health Sciences. She has received an honorarium from the American Academy of Allergy, Asthma, and Immunology.