Not unexpectedly, diphtheria vaccination does not receive the same media coverage as COVID-19 or seasonal flu, but it and the disease itself is worth knowing more about. There are several vaccines available that offer immunity against diphtheria, all of which protect against other diseases:

•    DTaP protects against diphtheria, tetanus, and pertussis (whooping cough) for children

•    DT protects against diphtheria and tetanus for children

•    Tdap protects against tetanus, diphtheria, and pertussis for adults

•    Td protects against tetanus and diphtheria for adults

Adults should keep their vaccinations up to date because immunity from childhood vaccines can wear off over time. You are also at risk for different diseases as an adult and vaccination is one of the most convenient and safest preventative care available.  

Every adult should receive a Tdap vaccine once if they did not receive it as an adolescent to protect against pertussis and then a Td (tetanus and diphtheria)  or Tdap booster shot every 10 years. The reason for the booster is that studies estimate that diphtheria toxoid containing vaccines protect nearly all people (95 in 100) for approximately 10 years.

In addition, women should get the Tdap vaccine each time they are pregnant, preferably at 27 through 36 weeks. The Centers for Disease and Prevention lists diphtheria, COVID-19 and influenza vaccinations as necessary for adults.  

All adults need immunizations to help them prevent getting and spreading serious diseases that could result in poor health, missed work, medical bills and not being able to care for family. It is important to know the difference between diphtheria toxoid (used for the vaccine) and diphtheria antitoxin. Toxoid is a preventative while the antitoxin is used for treatment when the disease is suspected. (A toxoid is a toxin modified to invoke an antibody response, but not capable of causing disease.)

The Disease

Diphtheria  was once a major cause of illness and death in children. It is transmitted from person to person, usually via respiratory droplets. The infection is caused by bacteria called Corynebacterium diphtheria.  Symptoms include sore throat, loss of appetite and fever. The most notable feature of the disease is the formation of a thick, gray substance called a pseudomembrane over the nasal tissues, tonsils, larynx and/or pharynx. The pseudomembrane is formed from waste products and proteins caused by the toxin secreted by the bacteria. This membrane sticks to tissues and may obstruct breathing.  

The toxin itself may travel to the heart, muscles, kidneys and liver where it may temporarily or permanently damage these organs.  Fortunately diphtheria is  currently not common in the U.S. but is endemic in many countries in Asia, the South Pacific, the Middle East, Eastern Europe and in Haiti and the Dominican Republic. Since 2016, respiratory diphtheria outbreaks have occurred in Indonesia, Bangladesh, Myanmar, Vietnam, Venezuela, Haiti, South Africa and Yemen.


Diphtheria is one of the least dangerous or one of the most dangerous diseases. It is one of the least dangerous when promptly treated with antitoxin; it is one of the most dangerous when the antitoxin treatment is not given, or is delayed or insufficient.

In the days before the antitoxin, one out of every three children who had diphtheria died. Now, if antitoxin is used on the first or second day of the disease 98 out of every 100 children recover. The sooner diphtheria is attended to the more certain is a cure.

In severe cases suspected to be diphtheria, the doctor always gives diphtheria antitoxin at once. This is a wise thing to do, because the disease goes on rapidly and a delay of 12 or 24 hours may be fatal. Besides, no harm is done, even if the disease proves not to be diphtheria. The antitoxin, although making some people uncomfortable for a day or two, never does any real harm.

Whenever antitoxin is given to a person ill with diphtheria it should be given in one dose, large enough and early enough.  The antitoxin is highly effective in treating diphtheria but it is not a replacement for active immunization using the toxoid.


The effective treatment for diphtheria – antitoxin – was discovered in 1890  by Shibasaburo Kitasato and Emil von Behring in Germany and used clinically one year later. The researchers immunized rats, guinea pigs and rabbits with attenuated  (weakened) forms of the infectious agents causing diphtheria and alternatively, tetanus. The sera produced by these animals were injected into non-immunized animals that were previously infected with the fully virulent bacteria. The ill animals could be cured through the administration of the serum.

With the blood serum therapy, Behring and Kitasato first used the passive immunization method in the fight against infectious diseases. The particularly poisonous substances from bacteria – or toxins – could be rendered harmless by the serum of animals immunized with attenuated forms of the infectious agent through antidotes or antitoxins. Pharmaceutical companies and public health agencies began to produce the new serum therapy in earnest in 1894. Von Behring received the 1901 Nobel Prize in Physiology or Medicine, the first one awarded in that field, for his discovery of a diphtheria antitoxin.

Max Sherman is a medical writer and pharmacist retired from the medical device industry.  His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns.  He can be reached by email at