Whole Cell Pertussis Vaccine May Help Protect Australian Infants Against Food Allergies

By Marilynn Larkin

January 22, 2020

NEW YORK (Reuters Health) - Australian infants who received the whole pertussis (wP) vaccine were less likely to be diagnosed with food allergies than those who received the acellular pertussis (aP) vaccine in a nested case control study.

"It is vital that young babies are vaccinated to protect them against whooping cough, and both the aP vaccine and the older wP whooping cough vaccines are proven to be safe and effective for doing this," Dr. Thomas Snelling of the Wesfarmers Centre of Vaccines and Infectious Diseases at the Telethon Kids Institute in Nedlands, Western Australia, told Reuters Health by email.

"What this study adds is evidence that an early dose of the wP vaccine might partially protect against food allergies, as well." He cautioned that "although the study included several hundred Australian children with food allergies, the study was not a controlled trial so more research is needed before the findings can be implemented."

Dr. Snelling and colleagues analyzed data on children born between 1997 and 1999, when Australia transitioned from wP to aP vaccines for scheduled doses at 2, 4, and 6 months old. Children diagnosed with IgE-mediated food allergy were individually matched to 10 controls by date of birth, socioeconomic level, and jurisdiction of birth.

Cases had 1) a documented clinical history of symptoms consistent with a typical IgE-mediated food allergic reaction within 1 hour of ingestion of a food; and 2) evidence of sensitization to the same food via either allergen skin prick test (SPT) >3mm or elevated serum-specific IgE >0.35kU/L.

Cases meeting these criteria were included in the analysis if 1) they received any pertussis vaccination by 16 weeks old; and 2) the onset of food allergy occurred after the first pertussis-containing vaccine and before the age of 15 years.

As reported in The Journal of Allergy and Clinical Immunology: In Practice, 579 children had IgE-mediated food allergy, of whom 502 (87%) had received a pertussis vaccine in the first 16 weeks. Of these, 24% had allergies to more than one food. A total of 5,018 controls were matched to the 502 cases.

The most common food allergies among cases were to peanut (52%), tree nuts (28%), and egg (20%).

The odds ratio of receiving the first dose as wP (rather than aP) among cases of food allergy compared to controls was 0.77.

Results of secondary analyses - any dose as wP versus aP-only, and wP-only versus aP-only - were "broadly similar."

Dr. Snelling said, "The next step is a carefully controlled study in which babies will be randomly assigned to receive either one dose of wP vaccine followed by two doses of aP vaccine, or to just have the usual schedule of three doses of the aP vaccine."

The team recently received funding from Australia's National Health and Medical Research Council to enroll up to 3,000 babies, who will be followed until the age of 12 months.

Dr. Anna Nowak-Wegrzyn, Director of Pediatric Allergy and Immunology at NYU Langone's Hassenfeld Children's Hospital in New York City, called the findings "extremely interesting and provocative."

"In the U.S., similar to Australia, aP was introduced in 1997 and doubling in peanut allergy was observed between 1997 and 2002," she commented in an email to Reuters Health. "If confirmed by future prospective clinical trials, this may represent a novel strategy to prevent development of food allergy."

"However," she said, "it is unlikely that aP vaccine is the sole factor driving the peanut allergy epidemic. The definition of food allergy...is very permissive and might have captured children who were not truly allergic."

Further, she noted, "The cases were ascertained at ages older than 10 years for 40% of the cohort, and first food allergic reaction was reported after age five in 30% of the cohort, raising questions about the persistence of the effect of immunization."

In addition, she said, "The analysis focused on food allergy without any information regarding the differences in allergic comorbidities such as eczema, asthma, inhalant allergies among cases and controls."

"It is important to recognize that early introduction of peanut into the diet of infants at risk for peanut allergy (i.e., severe eczema and/or egg allergy) has been shown to reduce risk of developing peanut allergy by 80%," she said. Updated NIAID guidelines (2017; http://bit.ly/375gwWW) and a statement from American Academy of Pediatrics (2019; http://bit.ly/2G25RjI) "recommend early introduction of peanut, egg and other foods in the first year of life, with special emphasis on at-risk populations, for whom testing and introduction should be done preferably as early as 4-6 months."

"While we are looking for additional strategies to mitigate food allergy risk, we must strive to implement the interventions that are readily available and proven to be efficacious," Dr. Nowak-Wegrzyn concluded.

SOURCE: http://bit.ly/375xqok The Journal of Allergy and Clinical Immunology: In Practice, online December 28, 2019.