Whooping cough cases are surging in the United States, with the number of infections five times higher than at the same time last year, according to preliminary data from the Centers for Disease Control and Prevention reported Friday.
Whooping cough cases are at their highest since 2014 and show “no signs of slowing down,” Dr. Susan Hariri of the CDC’s National Center for Immunization and Respiratory Diseases said Friday at a meeting of experts advising the U.S. announced. Food and Drug Administration on vaccine decisions.
This year’s surge in cases indicates the disease, also known as pertussis, has returned to pre-pandemic levels.
Even before the coronavirus pandemic began, cases of whooping cough were on the rise in the United States. Vaccines currently in use provide strong initial protection, but their effectiveness wears off after two to three years.
“We know there’s not a very good whooping cough vaccine,” Dr. Archana Chatterjee, a pediatric disease expert and dean of the Chicago School of Medicine, said at the conference.
“These vaccines have served us well for decades, but they don’t work as well as they used to,” said Chatterjee, a member of the FDA’s Vaccines and Related Biological Products Advisory Committee. .
The committee met on Friday to ask whether it’s time to allow drug companies to intentionally administer pertussis to people as a primary test for a vaccine, a type of study called a human challenge test. We debated whether or not there was.
Number of pertussis cases has increased for decades
As with many infectious diseases, the number of pertussis cases has fallen to unusually low levels during the pandemic as people limit social interactions and take other precautions to protect themselves from COVID-19. I did.
In 2020, the number of pertussis cases in the United States was approximately 6,000, but in 2021 that number decreased further to approximately 2,000. The number of cases in 2022 was about 3,000, compared to about 5,000 last year.
According to the CDC’s National Notifiable Disease Surveillance System, there have been 14,569 cases in the United States this year, compared with 2,844 during the same period last year.
Whooping cough begins with symptoms similar to the common cold, including a runny nose, sneezing, a slight fever, and a scratchy cough. After 1 to 2 weeks, the infection moves to a new stage, resulting in a severe generalized cough.
These coughing attacks can be severe enough to cause patients to vomit or break ribs, and are often accompanied by whistling sounds as they try to catch their breath. Antibiotics can treat the infection, but only if it occurs within the first few weeks before the tiring and painful cough develops. In that case, the only treatment is comfort care with plenty of rest and hydration until the infection resolves.
Unvaccinated infants and adults are at greatest risk of serious infection and, in rare cases, death. However, doctors are increasingly seeing vaccinated people who are still suffering from infectious diseases.
By age 6, young children usually receive five doses of the whooping cough vaccine, called DTaP or TdaP, which also protects against tetanus and diphtheria. Booster vaccinations are recommended for children aged 11 or 12 years. Pregnant women are also recommended to be vaccinated against infectious diseases, and adults are supposed to receive booster shots every 10 years.
Hariri said pertussis vaccination rates in the United States are high at about 90% and have not declined as they have in some other countries during the pandemic.
Despite this, the number of infected people continues to increase.
Vaccine protection is waning
The increase in cases is not fully understood. Dr. Todd Merkel, associate director of research in the FDA’s Office of Vaccine Research and Review, said in a presentation to the committee on Friday that there is evidence that it may be due to changes in the bacteria that cause the infection.
In the 1990s, the United States changed the type of vaccine it used to prevent whooping cough, moving from whole-cell vaccines that caused children to experience sudden fevers and other alarming symptoms after being vaccinated, to newer vaccines that did not cause as many reactions. I did. It also had less protection and didn’t last very long.
Merkel said other countries that have switched to new vaccines are also seeing a rise in infections.
Experts believe infections continued to spread because the new vaccines provided incomplete protection. It also caused bacteria to mutate to escape the immune response caused by vaccination.
Chancellor Angela Merkel said Friday that 90% of bacterial strains cultivated to infect humans in the United States involve mutations that evade vaccine protection.
For young children vaccinated against pertussis, protection now wears off rapidly, sometimes after 2 to 3 years, well before the age of 11 when a booster shot is recommended.
Regulators consider human stress testing
Infants are most at risk for severe disease, but older children and teens are increasingly infected as their defenses become weaker.
Therefore, a more effective and durable pertussis vaccination with fewer side effects is being sought.
However, testing new vaccines has been difficult because whooping cough has a cycle of outbreaks every three to five years, and researchers cannot predict when or where a surge will occur. Manufacturers need large numbers of infected people to test vaccinations.
Enter human subject research.
In some ways, whooping cough is an ideal infectious disease to test in a human challenge model. In the early stages, it is treatable with antibiotics, which protect research volunteers from harm.
On the other hand, most people have few symptoms in the early stages. While researchers can measure the vaccine’s ability to prevent mild early symptoms and whether it can prevent the bacteria from colonizing the nasal passages, the pertussis challenge model shows how well the vaccine protects against severe disease. It is not possible to directly measure whether this is possible. The goal of most vaccines.
Researchers also don’t know what immune factors indicate that people are protected against whooping cough, so they’re wondering if people are getting at least as much protection as the approved vaccines. You can’t even measure a strategy called bridging.
On Friday, Canadian and British institutions released a model for how to conduct pertussis challenge trials.
FDA advisers were then asked whether they thought this type of trial would measure the right things, and if so, whether it would provide enough evidence on which to base vaccine approval.
The laboratory model received mixed reactions from experts. On the one hand, they said the approach is exciting and will certainly speed up the testing of new vaccines. On the other hand, we were not sure whether these studies were sufficiently calibrated.
“I’m very supportive of this. I’m not entirely sure we’re there yet,” said Melinda, deputy director for vaccine policy and clinical partnerships at the CDC’s National Center for Immunization and Respiratory Diseases. Dr. Wharton said.
