Tetanus Vaccine: What is it? How does it work? Proof of Efficacy, Duration of Immunity and Myths Related to This Vaccine

Tetanus, also known as lockjaw, is unique among vaccine-preventable diseases in that it is not infectious from person to person.

Therefore, herd immunity does not provide protection for those who are not vaccinated.

Almost all reported cases of tetanus occur in people who have never been vaccinated or completed a primary series but have not received a booster in more than 10 years.

There are an estimated 800,000 to 1,000,000 deaths from tetanus each year, and about 50% of these are attributed to neonatal tetanus.

The tetanus vaccine, also known as tetanus toxoid (TT), is an inactivated vaccine used to prevent tetanus. During childhood, five doses are recommended, with a sixth administered during adolescence. Additional doses are recommended every 10 years.

After three doses almost everyone is initially immune. In those who are not up-to-date on their tetanus vaccination, a booster should be given within 48 hours of the injury. In those with high-risk injuries who are not fully immunized, tetanus antitoxin may also be recommended.

Making sure pregnant women are up-to-date on their tetanus shot, and otherwise immunizing them can prevent neonatal tetanus.

The vaccine is very safe, even during pregnancy and in people with HIV / AIDS . Redness and pain at the injection site occur in 25% to 85% of people.

Fever, tired feeling, and minor muscle aches occur in less than 10% of people. Serious allergic reactions occur in less than one in 100,000 people.

Various vaccine combinations include tetanus vaccine, such as DTaP and Tdap, which contain diphtheria, tetanus, and pertussis vaccines, and DT and Td, which contain diphtheria and tetanus vaccines.

DTaP and DT are given to children under the age of seven, while Tdap and Td are given to children seven years of age and older. Lower case d’s and p’s denote lower resistance of diphtheria and pertussis vaccines.

The tetanus vaccine was developed in 1924 and became available in the United States in the 1940s. Its use resulted in a 95% decrease in the rate of tetanus. It is on the World Health Organization’s Essential Medicines List, the most effective and safest medicines needed in a health system.

The wholesale cost in the developing world is between $ 0.17 and $ 0.65 per dose as of 2014. In the United States, a course of tetanus vaccination ranges from $ 25 to $ 50.

How does the preventive vaccine work?

The tetanus toxoid vaccine was marketed in the US in 1938, but it was not widely used until the military introduced routine vaccination in 1941.

The tetanus vaccine contains inactivated tetanus toxoid. This is prepared by treating the tetanus toxin chemically (usually by formaldehyde) to render it non-toxic without losing its immunogenic properties. The toxoid is concentrated, purified, and absorbed in a suitable adjuvant.

Tetanus toxoid immunization stimulates the body to create protective antibodies against tetanus toxin.

The amount of antibody produced is measured in international units (IU / ml). Based on animal studies, toxin antibody levels greater than 0.01 IU / ml have been estimated to be sufficient to protect against tetanus. This estimate has been confirmed in clinical reports.

After receiving primary doses of the vaccine, antibody levels far exceed protective levels of 0.1 IU / ml. However, antibodies decrease over time, and a booster every 10 years is recommended.

It is also recommended that anyone who receives a wound that is neither clean nor minor and who has not received a booster in over five years should receive one.

The vaccine is almost 100% effective in preventing tetanus, and almost all reported cases of tetanus are found in people who have never been vaccinated or who completed a primary series but did not receive a booster in the previous 10 years.

Vaccine efficacy test

The following historical studies and reviews shed light on the effectiveness of the vaccine:

A double-blind, randomized, controlled trial in rural Colombia demonstrated that tetanus toxoid administered to women of childbearing age reduced neonatal tetanus cases by 100% compared to controls. Similar studies report 70% to 100% effectiveness of the vaccine in preventing neonatal tetanus.

In 1942, German scientists Wolters and Dehmel were immunized with tetanus toxoid and achieved protective antibody levels of up to 0.01 IU / ml. They then injected themselves with “two or three fatal doses” of tetanus toxin, without problems.

Tetanus mortality in US troops dropped dramatically in WWII compared to WWI due to routine tetanus immunization of soldiers prior to WWII.

In World War I, 70 out of 520,000 wounded US soldiers contracted tetanus (13.4 per 100.00). In World War II, the number dropped to just 12 tetanus cases among 2.73 million wounded US soldiers (0.44 per 100,000). Only 4 of the 12 cases had been vaccinated.

A similar experience was reported in the British Army. In contrast, the German army had not been immunized against tetanus and spies reported 80 cases of tetanus among German troops during the Normandy invasion alone.

That figure may be very conservative as there were 53 cases of tetanus among German POWs in American hands in the UK during the period 7 September to 2 October 1944.

The tetanus vaccine was added to the routine childhood immunization program in 1944 because of:

  • The success of tetanus immunization campaigns in the army.
  • Wide distribution of spores of C tetani.
  • High fatality rates from tetanus.
  • Frequent and severe reactions to tetanus antitoxin as a form of treatment, which also had limited efficacy.

Duration of vaccine-induced immunity

Although a tetanus booster is recommended every 10 years, vaccine-induced immunity can last for more than 10 years. Studies in Denmark indicated that a primary series of three doses of tetanus immunization led to protective levels of antitoxin for more than 25 years in 72% of recipients.

These studies have suggested that a 20-year booster may be enough to maintain immunity. Other studies have suggested that further testing of tetanus immunity is not necessary until people reach 50 years of age.

Serological surveys of tetanus antibodies suggest that susceptibility to tetanus increases with age as a result of missing booster doses.

The age distribution of tetanus in developed countries reflects this. A survey conducted in the United States between 1998 and 2000 revealed that 75% of deaths from tetanus occurred in people 60 years of age or older.

The immune response to the tetanus vaccine is not compromised by the presence of passively acquired antibodies.

Current myths against the vaccine

Myth 1: You can’t get tetanus from a bleeding wound.

This is incorrect. Tetanus spores can survive in highly oxygenated environments (they live in the soil and intestines, for example).

Once they enter the body through a wound and find a favorable anaerobic environment in the dead or injured tissue, they germinate, mature to the vegetative form of C tetani (which is anaerobic), and release toxins.

One of the toxins produced, tetanolysin further damages the surrounding tissue and helps maintain an anaerobic environment for spore germination.

Myth 2: If I just clean my son’s wounds, he will be fine.

Wound cleansing is always a good idea. But nevertheless:

Wounds begin to heal within 20 minutes of an injury. C tetani can lodge deep in a wound, while the outside of the wound has begun to heal and dry out. Wound cleansing may not reach all affected tissues.

The spore format of C tetani is very resistant. It can only be inactivated by placing in a solution of carbolic acid, formalin, chloramine or hydrogen hyperoxides for 15-24 hours or by heating at 120 ° C for 15-20 minutes.

Only after the spores have germinated and matured to the vegetative form of C tetani, does the bacterium become sensitive to heat and light.

Up to 50% of tetanus cases occur after indoor injuries that are not considered serious enough to seek medical treatment. In 15-25% of cases, there is no evidence of a recent wound.

Myth 3: I can always give my child the IGT vaccine if he develops tetanus. Treatment with IGT is preferable to the tetanus vaccine.

IGT (Tetanus Immune Globulin) contains antibodies to tetanus derived from donated human or animal blood, and is used in the treatment of tetanus. However, IGT is only recommended in life-threatening conditions as it has the following disadvantages:

As a blood product, IGT can lead to serious allergic reactions, including anaphylactic shock. IGT derived from animal blood often produces allergic side effects, such as anaphylaxis and serum sickness.

IGT carries the risk of transmitting other infectious agents such as hepatitis and HIV. Donor screening has reduced, but not completely eliminated, this risk:

Protection through donated antibodies is short-lived. IGT produced from animal serum lasts 2 days, while IGT from human serum lasts 24-30 days. Therefore, the IGT vaccine would need to be rerun for each and every suspected tetanus lesion. Protection through tetanus vaccination lasts, on the contrary, 10 years or more.

Myth 4: There is no evidence that the vaccine works.

The vaccine is almost 100% effective in preventing tetanus, and almost all reported cases of tetanus are found in unvaccinated individuals.