Can Hib Vaccine Cause Asthma?
by Heidi White
Can the Haemophilus influenzae type b (Hib) vaccine cause asthma or allergy? I am not aware of any human studies that have specifically looked at the effect of Hib vaccine on asthma. However, a Swiss study1 found that invasive Hib infection (epiglottitis) could possibly be linked to an increase in the rate of asthma and allergies (OR 4.8). There may be a few explanations for this. Firstly, the treatment of a Hib infection with antibiotics, such as cephalosporins (eg cefotaxime or ceftriaxone), may by itself increase the risk of asthma.2 And secondly, cell wall components from the Hib bacteria may also be a cause of asthma.
If invasive Hib infection is able to cause asthma then it may also be possible that the Hib vaccine could also have a similar effect. Animal studies have provided various mechanisms for why this could occur:
a) A nasal Hib vaccine has been shown to stimulate Th1 and Th2 cells in mice.3 If the Th2 side of the immune system is over stimulated, then this can increase the risk of asthma and allergy.
b) Hib vaccination in rats has been shown to enhance histamine levels with a corresponding increase in the number of eosinophils.4-7 Eosinophils (white blood cells, used to fight infection) will proliferate and accumulate in the airways under stimulation by interleukin-5 (IL-5), a cytokine produced by Th2 cells. Eosinophil accumulation is also evident in the dermis of the skin seen in people with atopic dermatitis (eczema).
c) Hib vaccination in rats has been shown to cause increased bronchoconstriction in response to histamine, possibly due to an increased reactivity of the para-sympathetic/cholinergic pathways.7,8
d) Studies in guinea-pigs have shown that Hib vaccination may impair the beta (b ) 2-adrenergic system by causing a blocking or desensitization of b 2 receptors, or by reducing the number of b 2 receptors in the lung.9-13 Inhibition of b receptors can lead to increased bronchoconstriction. It is thought that the polysaccharide component of the bacterial cell wall may be responsible for this effect.14 HibTitre vaccine contains purified polysaccharide (PRP), from the capsule of the Hib bacteria, which is linked to a diphtheria carrier protein. PedvaxHIB vaccine contains PRP linked to a meningococcal protein.
It would be interesting to see the results of a human study that specifically examines the effects of Hib vaccine on the incidence of asthma and allergy.
Journal articles--Hib vaccine & asthma[Vaccination]