According to some studies, systemic infections such as measles, hepatitis A and tuberculosis infections prevent allergies and asthma. This is explained by the fact that some bacterial and viral infections shift the immune response towards Th1.
BCG vaccination, however, does not prevent allergies and asthma.
Recruits in Italy, who had antibodies for hepatitis A, suffered from asthma and allergic rhinitis 2 times less often, than the soldiers who did not have antibodies. Recruits, who had older brothers, also suffered from allergic diseases less frequently, which means that hepatitis A is not the only infection that decreases the risk of allergic diseases.
Hepatitis A was an endemic disease in Italy in the 1970s. It was usually an asymptomatic childhood disease.
Other studies in recent decades also reveal an inverse relationship between hepatitis A antibodies and allergies in different countries. In the 1970s in the USA, hepatitis A antibodies were more often detected in the older generation than in the younger one, whereas younger generation had more atopic diseases.
Children who did not have hepatitis A antibodies suffered from asthma and allergic rhinitis 9 times more often. Those who did not have hepatitis B antibodies suffered from allergic diseases 5.9 times more often. More: .
Varicella at the age under 8 years is associated with the decrease in the risk of asthma by 88%, allergic rhinoconjunctivitis by 84%, atopic dermatitis by 43%, allergic sensitization by 89%.
In those who have been sick with varicella, the level of IgE (antibodies responsible for allergic reactions) remains low for more than 10 years after the disease.
9% of children in USA suffer from asthma, and 17% suffer from atopic dermatitis.
Having a herpes type infection (including varicella) in the first 3 years of life is associated with a 50% decrease in the risk of asthma.
Having 5-7 viral infections in the first 3 years of life is associated with a 68% decrease in the risk of asthma, and 84% decrease in case of 8 and more viral infections.
Having rhinitis two or more times during the first year of life decreases the risk of asthma by 48%, and the risk of wheeze by 40%. Having rhinitis also decreases the risk of allergies.
In an analysis of 11,000 children who received a whole-cell vaccine in Canada, those who received the first dose of the vaccine two months later than usual developed asthma far less often (2-fold lower chance). Furthermore, those who received all three doses of the vaccine later in childhood had a 2.5-fold lower risk of developing asthma.
This phenomenon is due to the fact that the immune reaction shifts towards Th2. The exact cause of asthma is not yet known, but according to one of the prevailing theories, asthma is caused by increased hygiene. When children grow up in an extremely sterile environment, they do not come into contact with bacteria. This leads to the production of IgE antibodies. These IgE antibodies are responsible for asthma, allergies, dermatitis, and other problems that are much more common in vaccinated children. This is because vaccinations shift immunity towards Th2, which happens directly (due to vaccine antigens), and indirectly (due to protection against bacteria).
The vaccinated had asthma twice as often as the unvaccinated. The authors believe that 50% of asthma cases (2.9 million) in US children and adolescents would be prevented if the DTP or tetanus vaccination was not administered. More: 
In vaccinated with whole-cell vaccine, the risk of allergy was 76% higher. In those who took antibiotics in the first two years of life, the risk of allergy was 2 times higher.
Taking one course of antibiotics increased the risk of developing an allergy by 85%, two courses of antibiotics increased the risk 3-fold, and three courses of antibiotics increased the risk 8-fold.
Those who had measles and had not received the vaccine, had a 45% lower risk of developing an allergy (note: in this case there was no statistical significance).
Those individuals who had been vaccinated with a whole-cell vaccine, had a 5.4-fold greater chance of developing asthma compared to unvaccinated individuals.
The study compares homeschooled children in four states of the USA. 405 vaccinated and 261 unvaccinated children.
Vaccinated children had chicken pox 4 times less often, whopping cough – 3 times less often and rubella – 10 times less often.
Vaccinated children had otitis media 4 times more often and pneumonia – 6 times more often.
Those vaccinated had allergic rhinitis 30 times more often. They had allergies 4 times more often, ASD – 4 more often, ADHD – 4 times more often, eczema – 3 times more often, learning disabilities – 5 times more often, neurological disorders – 4 times more often. Vaccinated children had any type of chronic illness 2.5 times more often.
Vaccinated children used allergy medicines 21 times more often, antipyretics – 4.5 times more often, ear-drainage tubes – 8 times more often. They went to see a doctor, due to illness, 3 times more often and were hospitalized 1.8 times more often.
Some more interesting results from this study: risk of neurological disorders associated with the use of antibiotics during pregnancy (2.3 times), use of medicine during pregnancy (2.5 times), prematurity (5 times), ultrasound (1.7 times), and ultrasound done more than 3 times during pregnancy – 3.2 times.
The number of neurological disorders in vaccinated children (14.4%) coincides with the CDC studies (15%). The number of learning disabilities also coincides (5.6% of the vaccinated children in this study, and 5% according to available statistics).
However, judging by this study, there is already 3.3% of autistic children among vaccinated, i.e. 1 in 30 children. But, perhaps, it is an overestimation, as it is likely that children with ASD are homeschooled more often. (According to the CDC 2.24% of children are with ASD, i.e. 1 in 45 in 2015 and 1 in 36 in 2017).
Vaccination of a premature baby is associated with a 14 times increase in the risk of neurological disorders.
New Zealand, 23 unvaccinated (against DTP and Polio) out of 1,256 10-year old children. Out of the vaccinated children 23% had asthma, 22% got consults on asthma, and 30% had allergies.
There wasn’t a single case of asthma, or consults on asthma, or allergies among the unvaccinated children.
Children vaccinated against tetanus or with the DTP vaccine had asthma twice more often, allergies – 63% more often, and sinusitis – 81% more often, than the unvaccinated ones.
Among the children vaccinated with the DTP vaccine, 56% had asthma, chronic rhinitis or dermatitis. Among the unvaccinated ones only 9% had those diseases.
This is a study I'd already mentioned in another chapter (Para. 10 in "Unvaccinated). Those who were vaccinated with MMR had 3.5-fold higher incidence of asthma, and 4.5-fold higher incidence of eczema.
Initial analysis of 10 articles (for a meta-analysis). According to indirect markers, infectious diseases are associated with a 20% reduction of risk of dermatitis, 30% reduction of risk of allergic rhinitis and 40% reduction of risk of asthma.