In late May, an outbreak of pertussis (whooping cough) was declared by the Lexington-Fayette Health Department in Kentucky. This small cluster of 21 cases, as of two days ago, is not an outlier. Outbreaks are occurring across the country. According to CDC data as of May 25th, there have been 4,876 cases of pertussis reported in the United States and U.S. territories, which is roughly three times more than the same period last year.
Rather than some new phenomenon, this increase likely represents a return to an unfortunate normal after a lull in cases during the early years of the pandemic. Though not as common as in the days prior to the roll out of an effective whole-cell vaccine in the 1940s, when pertussis was reported around 200,000 times per year in the United States, this horrid respiratory infection has always been more persistent than other vaccine-preventable infections like measles, polio, and rubella. But we did appear to have it on the ropes at one point.
After a nadir of just over 1,000 cases in 1976, cases began to increase as more parents refused the vaccine because of concerns of permanent neurologic injury that were ultimately proven to be false. Another reason for higher numbers was the switch from a more effective whole-cell vaccine to an acellular vaccine for infants in 1991 out of an abundance of caution and in the hopes of increasing vaccine uptake. Despite numerous studies confirming that the safety concerns over the whole-cell vaccine were largely exaggerated, there are no plans to resurrect it and additional booster doses every ten years will continue to be necessary to maintain decent immunity.
The need for a booster throughout adulthood means that a large percentage of people have minimal if any immunity to pertussis. For a variety of reasons, such as limited access to care in certain populations, not seeking regular care even when it is available, and, of course, refusal of the shot when offered, there has been a large reservoir of unprotected adults. These individuals are capable of spreading the virus to the infants and high risk adults who are more likely to suffer serious outcomes or even die.
Now back to the numbers.
As I mentioned earlier, the pace of pertussis cases so far this year is tracking with a typical pre-pandemic year, and not a bad one at that:
| 2000 | 7,867 |
|---|---|
| 2001 | 7,580 |
| 2002 | 9,771 |
| 2003 | 11,647 |
| 2004 | 25,827 |
| 2005 | 25,616 |
| 2006 | 15,632 |
| 2007 | 10,454 |
| 2008 | 13,278 |
| 2009 | 16,858 |
| 2010 | 27,550 |
| 2011 | 18,719 |
| 2012 | 48,277 |
| 2013 | 28,639 |
| 2014 | 32,971 |
| 2015 | 20,762 |
| 2016 | 17,972 |
| 2017 | 18,975 |
| 2018 | 15,609 |
| 2019 | 18,617 |
| 2020 | 6,124 |
| 2021 2022 2023 | 2,116 2,388 5,611(provisional) |
https://www.cdc.gov/pertussis/downloads/pertuss-surv-report-2023_PROVISIONAL.pdf
There is good reason to be concerned, however. Cases of pertussis during the peak of the pandemic almost certainly had to do with more distancing and the use of other protective measures. It certainly wasn’t because of more people being vaccinated. And as more people act as if everything has returned to normal, cases will return to pre-pandemic numbers and will likely be worse because of the general increase in anti-vaccine sentiment that has emerged because of largely partisan propaganda and irrational pushback against the COVID-19 vaccines.
Pertussis cases are also on the rise around the world now that the pandemic-related effects are waning:
In England, provisionally there were 4,793 laboratory confirmed cases of pertussis reported to the UK Health Security Agency (UKHSA) between January and April 2024 with 555 cases in January 2024, 920 in February, 1,430 in March and 1,888 cases in April (Figure 1). This compares with 858 (provisional) laboratory confirmed cases of pertussis reported in 2023. There have been 8 reported deaths in infants who developed pertussis between January and April 2024.
https://www.gov.uk/government/publications/pertussis-epidemiology-in-england-2024/confirmed-cases-of-pertussis-in-england-by-month
And:
China recorded over 32,000 cases of pertussis in just the first two months of 2024 — a 20-fold increase from a year ago. The Philippines, the Czech Republic, the Netherlands and many other places have also reported a surge in cases.
https://www.bloomberg.com/news/newsletters/2024-04-15/whooping-cough-makes-a-return-even-in-the-vaccinated
Are you up to date with your pertussis vaccine? If not, get on that…please. You are significantly reducing the risk of a really bad illness if you are generally healthy, and hospitalization or even death if you aren’t. And you might save the life of someone else, like a precious little baby. There is also the added benefit of being protected from tetanus when you get your pertussis booster because it’s a combo shot. And who wants that?