What is the TDAP vaccine?
The TDAP vaccine is a vaccine that provides immunity against three diseases:
- tetanus (lockjaw),
- diptheria, and
- pertussis (whooping cough).
The vaccine is not live, meaning it cannot cause these diseases. Vaccination provides the body's immune system a "practice target", to which the immune system mounts a response and creates antibodies. Therefore, when the vaccinated individual encounters a live pathogen, their immune system will be ready to attack and neutralise the pathogen before it causes disease.
The TDAP vaccine became available in 2005 for older children and adults - before 2005, there was no vaccine for pertussis for anyone over 6 years of age [1, 2].
Who should get the TDAP vaccine?
The TDAP vaccine is indicated for children aged 7 and older, adolescents and adults.
Adolescents should receive a single dose of TDAP, preferably at 11 or 12 years of age.
Pregnant women should get a dose of TDAP ideally during every pregnancy, preferably early in the third trimester. This can protect the child from pertussis.
Adults that have never received a dose of TDAP vaccine should do so promptly. Furthermore, adults should receive a booster dose of either TDAP or a specific booster vaccine Td every 10 years, or after 5 years in the case of experiencing a severe or dirty wound or burn [2].
What does TDAP protect against?
Tetanus
Tetanus is a disease caused by the bacterium Clostridium tetani, which lives in the soil, and can infect the patient through cuts, burns, and other wounds. Tetanus is often referred to as lockjaw because tightening of the jaw muscles is one of the most common signs of this infection. Tetanus can lead to serious health problems, including muscle spasms, ultimately resulting in inability to breathe [2].
Diphtheria
Diphtheria is a disease caused by strains of bacteria that are typically transmitted through respiratory droplets, coughing, or sneezing. The disease typically affects the respiratory system, manifesting with symptoms such as generalised weakness, sore throat, mild fever, and swollen glands in the neck. Diphtheria can progress to difficulty breathing, heart failure, paralysis, and even death [2].
Pertussis
Pertussis, also known as whooping cough, is a highly contagious respiratory tract infection, caused by the bacterium Bordetella pertussis. Pertussis can cause uncontrollable, violent coughing that makes it hard to breathe, eat, or drink. The disease is particularly aggressive in babies, causing a severe pneumonia, convulsions, brain damage and death. The cough can be so aggressive that broken ribs have been reported [2].
Side Effects of the TDAP Vaccine
The TDAP vaccine is generally safe for infants, older children and adults. However, as with all vaccines and therapeutics, side effects can occur. With the TDAP vaccine, these side effects are usually mild and resolve within a few days [1, 3, 4, 5].
Common side effects include:
- mild pain, redness or swelling at the injection site,
- fatigue,
- generalised body pain,
- nausea, vomiting or diarrhea,
- mild fever and/or chills [1, 3, 4, 5].
In rare cases, the side effects can be more serious, including severe swelling, pain or bleeding at the injection site, a high fever, or an allergic reaction. Symptoms of the allergic reaction can include include hives, swelling of the face or throat, difficulty breathing, rapid heart rate, and dizziness.
If you notice any severe symptoms after being vaccinated with the TDAP vaccine, you should seek medical attention immediately and promptly [1].
Accidentally got TDAP vaccine twice: What now?
Generally, getting two doses of the TDAP vaccine is regarded as safe. Individuals who received repeated Tdap doses did not have significantly elevated risks of medical visits for various conditions, including seizures, cranial nerve disorders, or limb swelling.
In a study involving 68,915 patients, it was found that those who received two doses of TDAP did not have a significantly elevated risk of medical visits for severe adverse effects or negative medical outcomes compared to those who received a subsequent dose of tetanus toxoid, reduced diphtheria (Td) vaccine, which is another vaccine that is used as a booster to TDAP [6].
A booster is a vaccine dose that is used to reinvigorate the immune response to the vaccine the patient got previously. This is needed due to the fact that immune responses dampen over time.
Another study involving 19-30-year-old participants who had received a booster vaccination with either TDAP or Td found that a second dose of TDAP was well-tolerated and immunogenic. The incidence of adverse events was similar across the groups, with only mild, common side effects being reported [7].
There is now also mounting evidence suggesting that TDAP vaccination should be administered with every pregnancy to protect the child from pertussis, as TDAP-specific antibody levels were found to be reduced at the second compared to the first delivery in a study on 27 pregnant women with two children. Therefore, a booster of TDAP may be required [8].
Another study involving 1330 adults examined using TDAP as a booster 8-12 years after the first vaccination. The study also concluded that the second dose of TDAP is effective at increasing the immune response and is safe and well tolerated [9].
How many doses of TDAP are safe?
In adolescents who have received 5 doses, even a sixth dose was found to be well-tolerated and highly immunogenic. Side effects were mild and their prevalence consistent with other vaccinations, including pain (63.6%), redness (51.7%), and swelling (41.4%) were the most frequently reported adverse events [5].