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Diphtheria: Causes, Symptoms, Vaccines and Recent Outbreaks

Last updated November 1, 2026

Diphtheria is a serious disease caused by a toxin made by some strains of the bacterium Corynebacterium diphtheriae. It mainly affects the nose and throat, and less often the skin. The toxin can also damage the heart and the nerves.

Vaccines prevent diphtheria, but a person needs several doses and later booster doses to build and keep immunity. Where vaccination falls, outbreaks come back.

What Causes Diphtheria?

The bacteria themselves are not the main problem. The toxin they make is what causes the serious effects of diphtheria. The toxin kills healthy tissue and can cause many serious health problems.

Some strains of C. diphtheriae do not make the toxin. They can still cause infections, but these are generally less serious and are not called diphtheria.

There are 2 main types of diphtheria:

  • Respiratory diphtheria is the most serious type. It happens when toxin-producing bacteria infect the nose and throat.
  • Skin (cutaneous) diphtheria happens when toxin-producing bacteria infect the skin.

How Diphtheria Spreads

Diphtheria most often spreads when a person with the bacteria coughs or sneezes. This releases small droplets that other people can breathe in. People can also get infected by touching open sores or ulcers caused by the bacteria.

Some people carry the bacteria without getting sick, but they can still pass it to others. Close contact raises the risk of infection. Close contact includes:

  • Living with a person who has diphtheria.
  • Being close together often.
  • Sharing saliva or other respiratory secretions.
  • Being exposed to fluid from open sores or ulcers.

Anyone who is not vaccinated, or is not fully vaccinated, is at risk. Natural disasters and conflict can damage health services and interrupt routine vaccination. Overcrowding and poor hygiene also raise the risk of infection.

Symptoms of Diphtheria

Symptoms usually begin 2 to 5 days after exposure to the bacteria. Typical symptoms include:

  • A sore throat.
  • A fever.
  • Swollen glands in the neck.
  • Weakness.

Within 2 to 3 days, dead tissue in the airway can form a thick, grey coating. The coating can cover the nose, tonsils and throat, and it can make it hard to breathe and swallow.

Complications

Most severe illness and deaths from diphtheria are caused by the toxin. Complications can include inflammation of the heart and nerves, kidney failure and nerve damage.

For unvaccinated people who do not get proper treatment, diphtheria can be fatal in around 30% of cases. Children younger than 5 years have a greater risk of dying.

See a healthcare provider right away if you or your child has a sore throat with a grey coating, swollen neck glands or trouble breathing.

Diagnosis and Treatment

Healthcare providers usually decide if a person has diphtheria by looking for common signs and symptoms. If they suspect respiratory diphtheria, they start treatment right away, without waiting for test results. Testing uses a swab from the back of the throat and nose, or from a skin wound.

Treatment depends on the type of diphtheria:

  • Respiratory diphtheria is usually treated with diphtheria antitoxin and antibiotics.
  • Skin infections are generally treated with antibiotics only.

The antitoxin stops the toxin from causing more damage to the body. Antibiotics kill the bacteria and help prevent spread to other people. WHO notes that many current strains of diphtheria resist some commonly used antibiotics.

Having diphtheria does not replace vaccination. A person who has had diphtheria should get the vaccine after the illness is over. Close contacts of a person with diphtheria should get antibiotics to prevent illness, and they should be vaccinated if they are not up to date.

Diphtheria Vaccines

Vaccination is the best way to prevent diphtheria. The vaccine is most often combined with vaccines for other diseases, such as tetanus, pertussis (whooping cough), Haemophilus influenzae, hepatitis B and inactivated polio.

In the United States, there are 3 combination vaccines that protect against diphtheria:

  • DTaP is for babies and children younger than 7 years. It also protects against tetanus and whooping cough.
  • Tdap is for older children and adults. It also protects against tetanus and whooping cough.
  • Td is for older children and adults. It also protects against tetanus.

The CDC Schedule

The CDC recommends diphtheria vaccination for everyone:

  • Babies get 3 shots of DTaP, at 2 months, 4 months and 6 months.
  • Children get 2 DTaP booster shots, at 15 to 18 months and at 4 to 6 years.
  • Preteens get 1 shot of Tdap at 11 or 12 years. Teens who missed it should get it at their next visit.
  • Adults get a booster every 10 years. After 1 dose of Tdap, adults can get either Td or Tdap.
  • Pregnant women get Tdap early in the third trimester of every pregnancy, mainly to protect newborns from whooping cough.

WHO Recommendations

WHO recommends that all children get 3 primary doses in infancy, plus 3 booster doses in childhood and adolescence, for long-term protection. Many countries do not yet give all of these boosters. Only 83 countries have all 3 WHO-recommended boosters in their national programs, and 42 countries have no boosters at all.

Side Effects

Most people who get a diphtheria vaccine have no serious problems. Mild side effects usually go away within a few days. They can include soreness or swelling where the shot was given, a fever, tiredness and a poor appetite. Serious reactions after DTaP, such as seizures or a very high fever, happen much less often.

Talk with a vaccine provider about your vaccination history, any allergies and any past reactions to a vaccine.

Recent Outbreaks

Diphtheria was common around the world before widespread vaccination began in the 1930s. Combination diphtheria vaccines were part of WHO’s Essential Programme on Immunization from its start in 1974. WHO says these vaccines prevented more than 90% of cases between 1980 and 2000.

Today, outbreaks are happening more often because of gaps in vaccination. No WHO region is completely free from diphtheria.

In Africa, WHO reported the following for the period from 1 January to 2 November 2025:

  • 20,412 suspected cases and 1,252 deaths across 8 countries in the WHO African Region: Algeria, Chad, Guinea, Mali, Mauritania, Niger, Nigeria and South Africa.
  • Nigeria reported the most cases, with 12,150 suspected cases and 884 deaths.
  • Guinea had the highest death rate among suspected cases, at 25.8%.
  • Women, children aged 5 to 18 years and young adults under 30 were the most affected. This shows that the gap in immunity goes well beyond early childhood.

A global shortage of diphtheria antitoxin and limited laboratory capacity have made the response harder. WHO assessed the risk as high for the African Region and low at the global level.

Coverage Today

In 2025, an estimated 85% of infants worldwide (110 million) received all 3 doses of a diphtheria-containing vaccine. That left 15%, or nearly 20 million infants, with no doses or an incomplete series. Coverage varies widely between and within countries.

The diphtheria vaccines used for children and adults are combination vaccines that also protect against tetanus, and some also protect against whooping cough. Gaps in routine vaccination also leave children open to measles. To learn more about long-established childhood vaccines, read about traditional vaccines.

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