A new recombinant pertussis (whooping cough) vaccine booster shows long-lasting immunity in a phase 2/3 clinical trial in Thailand. This is good news in improving the effectiveness of the pertussis vaccine.

Recently, several pertussis outbreaks in the USA have been linked to vaccine hesitancy and waning immunity from the pertussis vaccine. A new vaccine may not affect vaccine hesitancy, but the clinical trial shows that the new pertussis vaccine booster could greatly improve long-term immunity to the disease.

This post will discuss what is pertussis and review the new data from the clinical trial.

What is pertussis?

Pertussis, or whooping cough, is an infectious bacterial disease caused by the Bordetella pertussis bacteria. The infection leads to uncontrollable coughing, with a “whooping” sound when you take a breath after the coughing spell. The disease is very contagious and although it is more common in infants and children, it can attack adults.

The coughing can be so difficult for infants and babies that they can choke or vomit. The coughing spells can be so problematic that it can be difficult for infants to eat, drink, or breathe.

The treatment for whooping cough is usually antibiotics. Early treatment is critical. It may make your infection less serious, and it can also help prevent spreading the disease to others.

Whooping cough is a dangerous disease with serious complications. According to the CDC, the most dangerous complications for babies younger than one year old who are treated in in the hospital are:

• 1 out of 5 (22%) get pneumonia (lung infection)
• 1 out of 50 (2%) will have convulsions (violent, uncontrolled shaking)
• 2 out of 3 (68%) will have apnea (slowed or stopped breathing)
• 1 out of 150 (0.6%) will have encephalopathy (disease of the brain)
• 1 out of 100 (1%) will die

About 1 in 3 babies younger than 1 year old who get whooping cough need hospital care. The younger the baby, the more likely that they will need hospital treatment.

There is one easy way to prevent pertussis, and it is the pertussis vaccine. The DTaP vaccine, which prevents diphtheria, tetanus, and pertussis, is usually given in five doses at 2 months, 4 months, 6 months, 15-18 months, and 4-6 years of age. Children older than six years and adults receive a different version of the vaccine called Tdap.

The vaccine is over 98% effective in preventing whooping cough in children who have received all five doses. Unfortunately, there is waning immunity from the vaccine especially compared to the previous versions of the vaccine that were available up through the 1990s. Nevertheless, even with waning immunity the vaccine is still very effective in preventing and reducing hospitalization from the disease.

Before widespread vaccination, whooping cough epidemics were a regular occurrence, with thousands of deaths reported each year. Once again, nearly all vaccine-preventable diseases are dangerous and with increases in cases of pertussis, we could go back to the pre-vaccine epidemics.

Unfortunately, the vaccination rate for DTaP has dropped from 95.3% in 2017-18 to 91.7% in 2023-24. That leaves the overall vaccination rate for pertussis at just above the herd immunity level. Worse yet, the non-medical exemption rate among US children entering school has nearly doubled from 2.0% to 3.7% in the same time frame.

Pertussis vaccine booster clinical trial

In a paper published on 2 December 2024 in the peer-reviewed journal JAMA Network Open, Punnee Pitisuttithum, MD, Vaccine Trial Centre, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand, and colleagues assessed antibody persistence five years after booster vaccination with either a recombinant or chemically detoxified pertussis vaccine. They followed 159 participants (mean age, 19.6 years; 56% women) who received the booster between 12- and 17-years-olds during a phase 2/3 clinical trial in Thailand.

Among the participants, 55 received the recombinant pertussis-only vaccine, 52 received the recombinant tetanus-diphtheria-pertussis vaccine (similar to the DTaP vaccine except with the recombinant pertussis component), and 52 received the chemically inactivated tetanus-diphtheria-pertussis booster vaccine (this is the typical DTaP vaccine). The participants were required to have received three doses of whole-cell pertussis vaccine in infancy.

The vaccine candidate, called Boostagen, is manufactured by BioNet-Asia Co., Ltd.

Here are the key results:

• Recombinant pertussis vaccines provided superior antibody persistence, with PT (pertussis toxin)-neutralizing antibody levels remaining 2.5- to 3-fold higher even after 5 years.
• Long-term seroprotection with PT-IgG antibodies was achieved in a higher proportion of participants receiving the recombinant pertussis-only (75%) and tetanus-diphtheria-recombinant-pertussis (56%) vaccines than in those receiving the chemically detoxified vaccine (27%).

Summary

These are great results that mean that the recombinant pertussis vaccine candidate greatly improves the pertussis component of the Tdap and DTaP vaccines.

However, there are a couple of caveats.

First, these are early results from an ongoing phase 3 clinical trial. We might get different results as we go along.

Second, I have no clue if BioNet-Asia will market this vaccine in the USA, Canada, Europe, or other countries. They may license the vaccine to companies that already manufacture the Tdap and DTaP vaccines in those countries.

Nevertheless, I find these results quite exciting and look forward to more news about how this vaccine might become part of the battle to defeat pertussis.

Citations

• Pitisuttithum P, Sirivichayakul C, Dhitavat J, Pitisuthitham A, Mansouri S, Pham HT. Pertussis Immunity 5 Years After Booster Vaccination With Recombinant Pertussis Vaccines. JAMA Netw Open. 2024 Dec 2;7(12):e2449182. doi: 10.1001/jamanetworkopen.2024.49182. PMID: 39636641; PMCID: PMC11621984.