Food allergy associated with lower SARS-CoV-2 infection risk

People with food allergies showed lower risk for SARS-CoV-2 infection, whereas those with obesity had a higher risk, according to a study published in The Journal of Allergy and Clinical Immunology.

Additionally, results of the perspective surveillance study showed asthma did not positively or negatively impact risk for SARS-CoV-2 infection.

“We know that development of childhood asthma is associated with severe early-life respiratory viral infection and that most asthma exacerbations, both childhood and adult, are related to respiratory virus infection,” Max A. Seibold, PhD, director of computational biology and the Wohlberg and Lambert Endowed Chair of Pharmacogenomics at National Jewish Health in Denver, told Healio.

“That prompted the question of whether there would be a similar kind of response to SARS-CoV-2 viral infection,” said Seibold, who also is a professor of pediatrics in the Center for Genes, Environment & Health at National Jewish Health. “To look at that, you really have to have a longitudinal study design, where you track individuals regardless of whether they have symptoms.”

The Human Epidemiology and Response to SARS-CoV-2 study involved 1,394 households with 4,142 participants who were tested for COVID-19 via nasal swabs every 2 weeks between May 15, 2020, and Feb. 1, 2021. Participants also completed weekly surveys, with periodic collection of blood samples.

Risk factors for COVID-19

During the study period, 147 households (10.5%) with 261 participants (6.3%) tested positive for SARS-CoV-2, including 6.1% of children aged 12 years and younger, 6.7% of adolescents aged 13 to 21 years and 6.2% of adults. The probability for infection appeared similar among children (14%), teens (12.1%) and adults (14%).

The study found no association between infection risk and current asthma (adjusted HR = 1.04; 95% CI, 0.73-1.46), eczema (aHR = 1.06; 95% CI, 0.75-1.5) or respiratory allergy (aHR = 0.96; 95%, 0.73-1.26).

“To be clear, there was no increase or decrease in risk among asthmatics, so they showed the same risk profiles as non-asthmatics,” Seibold said.

Participants with food allergy (31.1% adults, 28.7% teenagers and 40.2% children), however, had a 50% reduced risk for SARS-CoV-2 infection (aHR = 0.5; 95% CI, 0.32-0.81).

“Food-allergic individuals have very high type 2 inflammation. In vitro, we’ve shown type 2 inflammation can decrease ACE 2 receptor levels,” Seibold said, as the researchers noted that SARS-CoV-2 uses the ACE 2 receptor to enter cells.

“It’s possible that in the airway of food-allergic individuals, the type of inflammation they have may be driving down receptor levels and, therefore, decreasing their infection risks,” Seibold said.

Participants with obesity or overweight (63% adults, 14.7% adolescents and 22.3% children) experienced a 41% increase in risk for infection (aHR = 1.41; 95% CI, 1.06-1.87), with each 10-point increase in BMI percentile increasing the risk for infection by 9% (aHR = 1.09; 95% CI, 1.03-1.15).

The researchers said that further studies are needed to understand this association between obesity and greater infection risk, as they suggested that the inflammatory environment may change as BMI increases.

Meanwhile, 44.6% of infections overall were symptomatic, with 73.1% of them involving at least three symptoms. Whereas 24.5% of the infections were symptomatic among children, 41.2% of the infections among adolescents and 62.5% of the infections in adults were symptomatic.

“There was a want in creating the study to try to understand transmission in households with children with and without asthmatic and allergic individuals and try to understand how common asymptomatic infection is across age groups,” Seibold said.

“We knew that there are high rates of asymptomatic infection among kids,” he continued. “But to see the really strong linear relationship between age and presence of symptoms was striking.”

Household transmission

The researchers also found an association between exposure to a symptomatic member of the household and an 87.39-fold (95% CI, 58.02-131.63) increase in infection risk, whereas asymptomatic members offered a 27.8-fold (95% CI, 16-45.03) increase in risk, with no associations due to age or sex.

Additionally, the probability of transmission to an individual member of the household was 41.2% (95% CI, 32.3-49) within the first 50 days, with 88.3% of household transmissions happening within 14 days of the first household infection.

“Since we were tracking symptomatic and asymptomatic infections, we were able to see all kinds of transmissions,” Seibold said. “I think the contagiousness of the virus was much higher than people recognize.”

However, each year increase in the average age of children or adolescents in the house was associated with a 21% decrease in the odds of being a transmitting household (adjusted OR = 0.79; 95% CI, 0.69-0.89).

Specifically, adolescents had a 6.15-fold (95% CI, 2.49-15.21) increase in odds of being non-transmitters relative to children and a 3.55-fold (95% CI, 1.56-8.08) increase in odds of being non-transmitters relative to adults.

The researchers further did not find associations between having a person with asthma (aOR = 0.64; 95% CI, 0.33-1.23), upper respiratory allergy (aOR = 0.71; 95% CI, 0.27-1.84) or eczema (aOR = 1.85; 95% CI, 0.65-5.21) in the household and transmission.

“Patients could be more at ease in the sense that individuals with asthma are not at higher risk for becoming infected than someone without asthma,” Seibold said. “There’s a lot of fear among the asthmatic community that they’re really highly susceptible.”

Households with food allergy had significantly lower odds for transmission (aOR = 0.43; 95% CI, 19-0.96).

Participants with overweight or obesity, though, had 55% lower odds of non-transmission (aOR = 0.45; 95% CI, 0.25-0.82).

“It really reinforces like how big of a factor inflammation plays in susceptibility to infection — both a positive and a negative effect,” Seibold said, adding that the study also emphasizes the highly contagious nature of the virus across multiple age groups as well as the significance of asymptomatic infection.

Next, the researchers will sequence the messenger RNA collected from the participants’ airway epithelial cells during their biweekly swabs, including swabs from individuals taken before, during and after infection.

“We’re going to look at the airway cell responses to infections between someone who has been symptomatically infected vs. asymptomatically infected. We’re going to look at childhood vs. teenage vs. adult infection,” Seibold said.

Additionally, the researchers will see if there are any expression profiles in the airway that could predict whether someone is likely to develop an infection as well as at how airway profiles change once infections have resolved.

“All of that is really exciting and only possible because of the longitudinal nature of this collection,” Seibold said.

Reference:

• Food allergy is associated with lower risk of SARS-CoV-2 infection. https://www.nih.gov/news-events/news-releases/food-allergy-associated-lower-risk-sars-cov-2-infection. Posted June 1, 2022. Accessed June 2, 2002.

For more information:

Max A. Seibold, PhD, can be reached at seiboldm@njhealth.org.