Immunizing older adults with the tetanus-diphtheria-acellular-pertussis vaccine (Tdap) to prevent pertussis (more commonly referred to as whooping cough) was found to be as safe as immunizing them with the tetanus and diphtheria (Td) vaccine, according to a study by Kaiser Permanente published in the journal Clinical Infectious Diseases.

Researchers examined the electronic health records of nearly 120,000 people ages 65 and older at seven U.S. health systems between Jan. 1, 2006, and Dec. 31, 2010.

The study looked at a number of medical conditions following Tdap vaccination and found that although there is a small increased risk of injection site reactions 1-6 days following Tdap vaccination compared to other time periods, they are no more common than those following Td vaccination.

Researchers also found that patients who had received a tetanus- or diphtheria-containing vaccine within the prior five years did not have a higher rate of reaction from the Tdap vaccine.

“Published data on the safety of the Tdap vaccine in persons 65 years and older is limited as the vaccine was initially not licensed for this age group,” said study lead author Hung Fu Tseng, PhD, MPH from Kaiser Permanente Southern California’s Department of Research & Evaluation. “However, as the number of elderly individuals receiving Tdap increases, evaluation of the safety of the vaccine in this population becomes essential.”

The study provides empirical safety data suggesting that immunizing adults 65 years and older with Tdap should not have negative health impacts. All adults 65 and older should receive Tdap to reduce the risk of pertussis in the elderly and people they come in contact with.

“Recent outbreaks of whooping cough and infant deaths are a reminder of how serious these infections are and that pertussis immunization is important, particularly since one of the most common sources of pertussis in infants is their relatives, including their grandparents” said Tseng. “These findings should instill additional confidence for clinicians serving older adult populations in recommending the Tdap vaccine as a safe way to reduce the risk of pertussis infections.”

According to the Centers for Disease Control and Prevention, the most effective way to prevent pertussis is through immunization. Five doses of a diphtheria, tetanus, and pertussis vaccine (DtaP) are recommended for infants and children starting at two months of age.

Since protection from the childhood vaccine may fade over time, a Tdap vaccine is recommended for preteens, teens, and adults. Tdap is especially important for expectant mothers and those caring for infants.

Pertussis is a highly contagious bacterial disease that causes uncontrollable, violent coughing and can be deadly in infants, especially those under two months of age who are too young to be vaccinated.

In 1976, there were just over 1,000 reported cases of pertussis in the United States; by 2010, it climbed to nearly 28,000 cases – the largest number of cases reported in the U.S. since 1959 when 40,000 cases were reported.

Between 2000 and 2005 there were 140 deaths resulting from pertussis in the United States.

This study is part of the Vaccine Safety Datalink (VSD) project, a collaborative effort between the CDC’s Immunization Safety Office and 10 health systems including Kaiser Permanente.

The VSD project was established in 1990 to monitor immunization safety and address the gaps in scientific knowledge about rare and serious events following immunization.

The research is also part of Kaiser Permanente’s broader efforts to deliver transformational health research regarding the safety and effectiveness of vaccines.

Earlier this year, Kaiser Permanente researchers found that the herpes zoster vaccine, also known as the shingles vaccine, is generally safe and well tolerated.

Another Kaiser Permanente study from this year found that vaccines for measles were not associated with an increased risk of febrile seizures among 4-6 year olds during the six weeks after vaccination.