Natural immunity

Meningococcal

Human immunity to the meningococcus, II. Development of natural immunity. 1969, Goldschneider, J Exp Med

As a result of asymptomatic colonization of meningococcus, meningococcus antibodies are produced within several weeks.
Infant under 6 months of age are protect by their mothers’ antibodies. Concentration of antibodies in the blood of infants is higher than in the blood of mothers.
Natural immunity is usually produced in childhood.

Haemophilus influenzae

Naturally acquired immunity to Haemophilus influenzae type B in healthy Cuban children. 2004, Toraño Peraza, Mem Inst Oswaldo Cruz

The authors analyzed 974 healthy unvaccinated children in Cuba and found that 99.7% of them had natural immunity to Hib by the age of 4-5. Natural immunity to Hib was also found in Finland (79%) and in India ( 80%). Therefore, WHO recommends that this vaccine be introduced into the national calendar only in countries that can afford it financially without taking resources from other important vaccines.
Here reported on the natural immunity to Hia in Aborigines in Canada. More: [1].

Tetanus

Naturally Acquired Immunity to Tetanus Toxin in an Isolated Community. 1985, Matzkin, Infect Immun

There is a complete medical consensus on that natural immunity against tetanus is impossible, and only a vaccine can prevent the disease.
The authors ran blood tests of two hundred randomly selected immigrants from Ethiopia to Israel and found tetanus antibodies in 98% of them. 30% of them had the level of antibodies that is considered protective (above 0.01 UI/ml). None of them have been vaccinated.
The amount of antibodies increased with age. The authors concluded that natural immunity is produced from continuous contact with the bacteria.

Tetanus

Tetanus immunity in kibbutz women. 1989, Leshem, Isr J Med Sci

Researchers ran blood tests of 120 randomly selected women living in Israeli kibbutzim. All of them had sufficient levels of antibodies against tetanus toxin, despite the fact that 12.5% of them had never been vaccinated.
Many of them were not fully vaccinated (from 6% among the young to 68% among the elderly).

Tetanus

Naturally acquired antibodies to tetanus toxin in humans and animals from the Galápagos islands. 1983, Veronesi, J Infect Dis.

The level of tetanus antibodies of 57 tested residents of Galapagos Islands was above the protective level. None of them had been vaccinated. Two of them have had tetanus in the past. This contradicts the accepted dogma that having had the disease does not give immunity.
They also checked nine animals (horses, cows, donkeys and a dog) and all of them had sufficient levels of antibodies.
The authors believe that immunity is produced by swallowing bacterial spores that multiply in the intestines. While the skin wounds act like booster vaccines.
It is reported here that most of the 59 unvaccinated people had protective levels of antibodies.
It is reported here that 80% of the 410 of unvaccinated Indians had antibodies in their blood.
The occurrence of natural immunity in 20 out of 48 children and adults in Mali is reported here.
It is reported here that out of 166 unvaccinated people only two did not have antibodies.

Tetanus

The tetanus bacillus as an intestinal saprophyte in man. 1922, Tenbroeck, J Exp Med

The answer to the question, how natural immunity is produced was already given back in the 20s of last century. Tetanus bacteria were found in the intestines of 35% of the 78 men tested in Beijing. Tetanus was a very rare disease in China in early 20th century (not counting the neonatal tetanus).
Researchers found tetanus bacteria in the patients’ stool even after they spent three months in the hospital on a virtually sterile diet. This can lead to a conclusion that tetanus bacteria multiply in the intestines.

Tetanus

Studies on the relation of tetanus bacilli in the digestive tract to tetanus antitoxin in the blood. 1923, Tenbroeck, J Exp Med

Continuing with the previous article. 26 people who had tetanus bacteria in their stool had antibodies in their blood.
Among the 30 people who did not have bacteria in their stool, 28 did not have tetanus antibodies either. The authors proved that tetanus bacteria multiply in human intestines. They also explained why despite the fact that a third of population have tetanus bacteria living in their intestines, they get sick with it very rarely, even after surgeries.
To check for the production of tetanus antibodies through their ingestion with food, one of the authors of the study swallowed a large number of bacteria (there were real scientists once!). The experiment had to be stopped, however, as he got constipation (it is unclear whether it was due to the ingestion of bacteria). The experiment on a monkey was more successful.

Tetanus

The immunity produced by the growth of tetanus bacilli in the digestive tract. 1926, Tenbroeck, J Exp Med

Guinea pigs that were fed tetanus bacteria developed antibodies in six months. There are many strains of tetanus bacteria, however, and the antibodies were produced only for the strain, which was fed to them. They did not get immunity from other strains. Those who were fed with several strains, developed immunity to all the strains.
In one of the experiments the authors infected the guinea pigs with tetanus and all but two of them died. It turned out, that those two pigs were accidentally placed with a male and both of them were pregnant. How did the pregnancy save them from tetanus remains unclear. They gave birth to healthy babies.
In addition, the authors report that it is widely known that the bacteria spores themselves are not enough to get infected (!). In order for the infection to occur some other irritating factor is needed. They used different materials as an irritant (a glass vial, among others). A vial filled with tetanus bacteria spores was inserted under the skin of guinea pigs and smashed. The fact that bacteria spores themselves are insufficient for infection also explains the fact that despite the prevalence of the bacteria, disease cases are extremely rare.
There is no connection between the amount of antibodies in the blood and immunity to tetanus. The authors conclude that the toxin antibodies play only a small role in the tetanus immunity, and that there is something else that protects against infection. They assume it is the [agglutininshttps://en.wikipedia.org/wiki/Agglutinin]. These agglutinins are specific – each bacteria strain has its own agglutinin.

Tetanus

Study of tetanus agglutinins and antitoxin in human serums. 1926, Coleman, J Infect Dis

The researchers ran blood tests of 104 California residents. Agglutinins to several strains of tetanus bacteria were found in the blood of 80% of them, but they did not have antibodies. The authors believe that tetanus bacteria were in the intestines of these people in the past, but did not survive there and thus they do not have the antitoxin.
Tetanus agglutinins have not been researched since then.

Tetanus

Human intestinal carriers of tetanus spores in California. 1926, Bauer, JSTOR

In four years from 1922 to 1925 in California, 245 cases of tetanus have been recorded. Mortality rate was 67%.
Among the 530 people in the study, the authors found bacteria in the intestines of 24%. They believe that the presence of tetanus bacteria in the intestines depends on the microflora, since they have always seen other types of bacteria along with tetanus bacteria, and did not see other bacteria, when the tetanus bacteria were absent.

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