Allergies are becoming more common, and the anti-vaccination movement, which will blame anything they don't like on vaccines, has a predictable scapegoat. Unfortunately for them, a new study provides evidence the “whole-cell” vaccine against whooping cough actually slows this rise. When Australia swapped to the new acellular vaccine, allergy rates jumped, not because the new vaccine induces allergies, but because the old one's protection was lost.
Whole-cell vaccines were the original tool used to bring whooping cough under control. They are effective in conferring fairly long-lasting protection against an occasionally fatal disease marked by its long-lasting painful cough. However, children injected with the vaccine often suffer fevers and become irritable immediately afterward, inspiring a search for something better. The acellular vaccine is now used in the majority of wealthy countries. Worldwide, however, the whole-cell's lower cost has seen it retain dominance as protector against this terrible disease.
The two vaccines stimulate different sorts of immune responses and Professor Tom Snelling of the Telethon Kinds Institute wondered if this might have consequences, with the switch possibly contributing to Australia's exceptionally high rate of allergies among children born in the last 20 years.
In The Journal of Allergy and Clinical Immunology: In Practice, Snelling describes a process to identify allergic children born around the time of the change-over and compare them with others born around the same time and in similar environments. Those given the whole-cell vaccine were 23 percent less likely to develop allergies than those who received the acellular version.
In an online media conference Snelling described the difference as evidence for the hygiene hypothesis, which attributes the rise in allergies to the cleaner environments in which children are now raised. Where the immune systems of earlier generations were exposed to many harmless microbes, we now protect children from these, leading to an unbalanced immune system more prone to allergic reactions.
The whole-cell vaccine induces an immune response that rebalances the immune response. Similar benefits have been attributed to the BCG vaccine against tuberculosis.
Snelling acknowledged that previous studies found no evidence for a difference in allergy rates between recipients of the two vaccines. However, he noted these used much smaller samples. Moreover, he argued his team made sure their subjects had real allergies, rather than other forms of food intolerances that are sometimes wrongly diagnosed as allergies.
Nevertheless, the study still had some weaknesses, which Snelling said will be addressed in a future controlled trial.
Snelling added that whether a reduced risk of allergies, if proven, is worth the temporary fever and other side effects is not a simple question and “a lot of things would have to happen” for Australia to switch back. Nations that are still using whole-cell, however, might be much less inclined to change.
In addition to spreading misinformation about the safety of both vaccines, anti-vaxxers can be expected to blame the acellular version for the rise. However, Snelling told IFLScience: “It’s important to understand that both the ‘acellular’ and the older ‘whole-cell’ vaccines are safe and very effective... whole-cell vaccines more closely resemble infection, and we believe this helps to train the developing immune system to tell the difference between dangerous bacteria and harmless substances like food. In this way, we believe whole-cell vaccines may have the added benefit of providing protection against food allergies.”
