Even before the Covid-19 pandemic, whooping cough cases were trending upward in the US, because the vaccines that are currently used offer strong initial protection that wears off after two or three years.
Whooping cough cases climbing for decades As with many infectious diseases, cases of whooping cough dropped to unusually low levels during the pandemic as people limited social interactions and took other precautions to defend against Covid-19.
Whooping cough starts with symptoms that look a lot like a regular cold: a runny nose, sneezing, a low-grade fever and a tickly cough.
That’s led to a hunt for better, more durable immunizations against whooping cough that also don’t cause as many side effects.
In some ways, whooping cough is an ideal infection to test in human challenge models.
According to preliminary data released on Friday by the US Centers for Disease Control and Prevention, whooping cough cases are five times higher in the US right now than they were at the same time last year.
Presenting the data on Friday at a meeting of experts who advise the US Food and Drug Administration on vaccine decisions, Dr. Susan Hariri of the CDC’s National Center for Immunization and Respiratory Diseases said that the number of whooping cough infections is at its highest since 2014 and “with no indication of slowing down.”.
The rise in cases this year indicates that the infection, also known as pertussis, is returning to pre-pandemic levels.
As a result of the current vaccinations providing strong initial protection that wears off after two or three years, whooping cough cases were trending upward in the US even prior to the Covid-19 outbreak.
The dean of the Chicago Medical School and an expert in pediatric diseases, Dr. Archana Chatterjee, stated during the meeting, “We know that we do not have very good pertussis vaccines.”.
As a representative of the FDA’s Vaccines and Related Biological Products Advisory Committee, Chatterjee stated, “These vaccines have done a yeoman’s job for us for many decades, but they are not doing the job as well as they used to do.”.
The committee convened on Friday to deliberate whether the time has come to permit drug companies to deliberately infect individuals with whooping cough as the main testing ground for their vaccines—a research method known as a human challenge trial.
Cases of whooping cough have been rising for decades.
Whooping cough cases fell to exceptionally low levels during the pandemic, as with many infectious diseases, as people avoided social situations and took other preventative measures to fend off Covid-19.
The number of pertussis cases in the US decreased to about 2,000 in 2021 from about 6,000 cases in 2020. Between 2022 and this year, there were roughly 3,000 and 5,000 cases, respectively.
The Nationally Notifiable Diseases Surveillance System of the CDC indicates that there have been 14,569 cases in the US so far this year, up from 2,844 cases at the same time last year.
Sneezing, runny nose, low-grade fever, and tickly cough are the initial symptoms of whooping cough, which are similar to those of a common cold. After a week or two, the infection progresses to a new stage that causes a strong, all-over cough.
Patients may break ribs or vomit during these episodes of extreme coughing, which are frequently accompanied by a whooping sound as the cougher tries to catch their breath. Only if the infection is discovered in the initial few weeks, prior to the onset of the excruciating, painful cough, can antibiotics be used to treat it. Until the infection clears up, the only course of treatment is comfort care, which includes lots of rest and fluids.
Those who are not vaccinated are most at risk of developing serious infections and, in rare cases, passing away. Yet vaccinated individuals with infections are also becoming more and more common in the doctors’ office.
By the time they are six years old, young children usually have received five doses of the DTaP or TdaP vaccine, which helps prevent tetanus and diphtheria in addition to pertussis. Children who are 11 or 12 years old should get boosters. Adults are expected to receive booster shots every ten years, and pregnant women are advised to receive the vaccination as well.
As opposed to some other nations, the United States has high pertussis vaccination rates (roughly 90%), which did not decline during the pandemic, according to Hariri.
The trend of rising infections has persisted in spite of this.
The benefits of vaccinations are diminishing.
It is unclear why there is a rise in cases. Dr. Tod Merkel, associate director of research in the FDA’s Office of Vaccines Research and Review, told the committee on Friday that there is evidence to suggest the infection may be caused by changes in the bacteria that causes it.
The US modified its pertussis vaccination regimen in the 1990s, switching from a whole-cell vaccine that gave children fever spikes and other concerning side effects to a more recent vaccine that gave less protection and lasted shorter.
Other countries that changed to the newer vaccines have seen cases increase too, Merkel said.
Experts believe that the infection has been able to spread because the newer vaccines have not provided enough protection. In order to evade the immune reaction brought on by the injections, it has also led to bacterial mutations.
90 percent of the bacterial strains that have been cultured from human infections in the US, according to Merkel’s statement on Friday, are now linked to mutations that allow the vaccine to evade its protective effects.
Protection from the pertussis vaccine now waned quickly in young children, sometimes after two or three years – well before the recommended booster shot age of eleven.
Regulations take human challenge studies into account.
While severe disease primarily affects babies, as protection wears off, infections in older children and teens are on the rise.
This has prompted research into developing whooping cough vaccinations that are both more effective and long-lasting while also minimizing side effects.
Yet because whooping cough outbreaks occur in large waves every three to five years and because scientists are unable to forecast the exact location and timing of the epidemic, testing new vaccines has proven challenging. To test their vaccines, manufacturers require a sizable population of infected individuals.
Let’s talk about human challenge studies.
Whooping cough is a perfect infection to test in human challenge models, in certain aspects. Antibiotics can treat it when it’s still in the early stages, sparing study participants harm.
However, in those initial stages, the majority of people don’t have many symptoms. Researchers can assess if the vaccine can stop bacteria from growing in nasal passages and prevent mild early symptoms, but the pertussis challenge models do not enable them to assess directly how well a vaccine may prevent severe disease, which is the main objective of most vaccines.
Researchers are also unable to assess whether individuals are receiving protection that is at least as effective as that offered by the licensed vaccinations, a tactic known as bridging, since they are unaware of the immune markers that may suggest a person is immune to whooping cough.
Canada and the UK labs showcased their models on Friday regarding how to run pertussis challenge trials.
Then, questions about whether these trials could measure the right things and, if so, whether they would yield sufficient data to support a vaccine approval were posed to the FDA advisers.
The experts had differing opinions about the models from the labs. They stated that this strategy was intriguing and would undoubtedly expedite the testing of novel vaccines. However, they weren’t certain that these studies had been sufficiently adjusted.
“I’m very in favor of this; I’m not sure if we’re quite there yet,” stated Dr. Melinda Wharton, the National Center for Immunization and Respiratory Diseases at the CDC’s associate director for vaccine policy and clinical partnerships.