Hay fever not linked to kids' immunizations

Routine childhood immunizations do not increase the likelihood that kids will develop hay fever, US researchers suggest.

"Suggestions that immunization influences allergic disease risk ... are of concern for vaccination policy," Dr. D. G. Cook, of St. George's Hospital Medical School, London, and colleagues write in the Archives of Disease in Childhood.

The researchers examined whether vaccinations in infancy influence the risk of hay fever using data from two large primary care databases in the UK - the General Practice Research Database and the Doctors' Independent Network.

A total of about 3500 hay fever cases were matched with similar but unaffected individuals.

The relatively few children that had not been vaccinated for diphtheria, tetanus and Pertussis (DTP) had virtually the same hay fever risk as the large percentage that completed DTP vaccinations by their fifth month.

As for measles, mumps and Rubella (MMR) immunization, unvaccinated children had slightly lower chances of having hay fever than those vaccinated in month 14, although the difference was not statistically significant.

The investigators found that with both DPT and MMR vaccination, children that got their shots late had about a 40 percent reduced risk of hay fever. The team suggests that this "may be explained by a third factor causing both postponement and reduced risk, such as intercurrent febrile illness."

Cook and colleagues also looked at anti-TB immunization with BCG vaccine, which is thought to protect against becoming allergic. However, that's not what they found. "Immunization with BCG by age 2 was associated with an increased risk of hay fever," they report.

Overall, the researchers conclude that their results should reassure parents and doctors, and they stress that no opportunity to immunize should be missed.

SOURCE: Archives of Disease in Childhood, June 2005.