A recent article in the journal Pediatrics reported a surge in cases of pertussis, commonly known as whooping cough. Unfortunately the article is only available to subscribers to the journal. Here is a link to a description of that article in a medical news service called Medscape. Pertussis is a bad disease. See below.
History of pertussis
Pertussis is caused by a bacterium, Bordatella Pertussis. Prior to the advent of pertussis vaccines, pertussis was one of the leading US causes of death of children under 5 years of age. There were over 200,00 cases and 9000 childhood deaths in the US from pertussis every year (a rate of 4.5 deaths per thousand children). Pertussis was especially lethal in infants, and was probably the leading cause of death in this age group. Worldwide, pertussis prior to vaccines was just as bad as in the US or worse. Worldwide there were 24.1 million cases and 160,700 deaths in children under five every year.
Epidemiology of pertussis
In un-immunized people pertussis is extremely infectious, almost as much as measles. One infected person on average infects 12-18 other people. In adolescents and adults pertussis is unlikely to cause death or hospitalization, but it is an extremely unpleasant disease. Older children and adults have paroxysms of coughing, followed by a loud, wheezing inspiration (the whoop of whooping cough). These symptoms can last for weeks or months. The coughing is sometimes so severe that people break ribs or develop hernias. Treatment with antibiotics is used to prevent transmission. Antibiotics are also given to contacts to prevent them from getting infected. Antibiotics do not have any effect on the length or severity of the disease. Those who have symptomatic pertussis just have to wait for it to go away. Here is an audio file of a child with pertussis. You should listen to it realize what a severe disease pertussis is. Let me warn you that it is distressing to listen to.
Pertussis vaccines
Whole cell pertussis vaccines
Whole cell pertussis vaccine combined with vaccines for tetanus and diphtheria was widely introduced and given to infants and children in the 1940’s. This was a highly effective vaccine. It not only prevented disease, but also prevented colonization and therefore stopped transmission of pertussis. It reduced the cases of pertussis by 75%. Unfortunately, the whole cell vaccine had rare but concerning side effects.These iincluded persistent crying, febrile seizures and hypotonic-hypoeresponive episodes (HHE). Children with HHE had sudden onset of reduced muscle tone, decreased responsiveness to verbal or other stimuli, and change in skin color (pallor or cyanosis) that occurred shortly after vaccination. These adverse events, though temporary were obviously distressing to parents. There were also rare cases of encephalopathy (Inflammation of the brain) that caused permanent disability. These cases were so rare that it was impossible to know whether these permanent disabilities were caused by the vaccine, or were simply associated but not causal. Controversy over whether the vaccine had any role in these cases continues even today.
Acellular pertussis vaccine
Because of the rare but distressing side effects of whole cell pertussis vaccine, a new vaccine was developed that had components of the pertussis bacterium, but not whole cells. This was called the acellular vaccine. This acellular vaccine had far fewer and milder adverse reactions than the whole cell vaccine. The combination vaccine is abbreviated DTaP (diptheria-tetanus-acellular pertussis). This is the vaccine used for children today. Unfortunately the acellular pertussis vaccine is less effective than the previous whole cell vaccine. It does prevent children from getting ill with pertussis, but it does not prevent colonization of the nose and throat. Children who are colonized in this way are not sick, but they are infectious and can pass on the virus to other children and adults. This keeps the bordatella pertussis bacteria circulating in communities.
Waning Immunity
Neither the whole cell nor the acellular vaccine provides lifetime immunity, unlike the Measles-Mumps-Rubella vaccines, which do provide lifetime immunity. Even people who have pertussis do not get lifetime immunity. Immunity from vaccines and infection wane over time. It appears that the acellular pertussis vaccine gives good protection from getting sick from pertussis for about 4 years, and starts to wane after that. The result is that we still see pertussis even in fully immunized children and adults starting about 5 years after the last routine immunization, which occurs at between 4 and 6 years of age. A booster TDaP is also recommended at around 12 years of age. This means that the most vulnerable children, that is children 5 or under are protected from getting ill from pertussis. Infants below 2 months of age (too early for vaccination) are protected by the recommendation that all pregnant women get a booster TDaP vaccine in the third trimester of every pregnancy. Anyone who is going to have extended contact with an infant under 2 months should also get a booster TDaP.
Risk of resurgence of severe pertussis
Bordatella pertussis continues to circulate in communities because of colonization of immunized children. Resistance to vaccinating children with DTap can quickly cause a resurgence of pertussis in infants and young children. This would be disastrous and is already happening. In 2024, there were 35,435 documented cases of pertussis across the U.S., including 655 in Colorado. That was a huge jump over the 7063 cases in all of 2023. Large states, including New York and California, logged high numbers of pertussis infections in 2024. So did some less-populated states like Idaho, Washington and Oregon, each of which reported more than 1,000 cases of pertussis. There were 10 deaths from pertussis in 2024. Cases are on track to be even higher in 2025.
Research on new pertussis vaccines
The search is on for a new pertussis vaccine that prevents colonization but that also does not cause the distressing side effects that happened with the whole cell pertussis vaccine. The best candidate at the moment is a live vaccine that has been genetically modified to eliminate the toxins produced by the bacterium. If and when approved this vaccine will be administered nasally. In rhesus monkeys it prevented colonization with bordatella pertussis and had no significant side effects. It is currently in phase 3 trials in humans.
Bottom Line
Pertussis is a serious disease and is life threatening to infants and young children. The severity and duration of pertussis are not affected by antibiotics that are given to limit the spread of the disease. The only effective treatment of pertussis is prevention through immunization. Acellular pertussis vaccine is much safer but also less effective than the old whole cell vaccine. It allows bordatella pertussis to continue to circulate in communities. Resistance to immunization of children has led to a marked increase in serious pertussis infections in 2024 with 10 deaths reported. Pertussis cases are on track to be even higher in 2025. A promising new attenuated live pertussis vaccine is in phase 3 trials and may soon be approved assuming research funding is not withheld by the Trump administration.