This year could shape up to be the worst year for whooping cough Washington has seen in over a decade.

State health officials counted 1,193 cases of whooping cough, or pertussis, across 31 counties as of Nov. 2, according to the Department of Health's most recent update. This time last year, the state had reported 51 cases.

Washington is not alone in its sharp rise of the highly contagious bacterial infection this year. It's been an usually bad year for whooping cough in the United States, which has counted more than 20,000 cases so far. Seven states, including Washington, have reported more than 1,000 infections.

"The surge in pertussis cases is a stark reminder of how critical vaccinations are in protecting our most vulnerable, especially infants for whom it can be life threatening," Dr. Tao Sheng Kwan-Gett, the state's chief science officer and a pediatrician, said in a statement.

Of the people who have gotten sick, 28 have been hospitalized, including 12 infants younger than 1 year old, according to DOH. More than 80% of cases were recorded among those under 18, with about 34% among those younger than 4.

The highest rates of infection are in Whitman, Clark and Chelan counties, which all reported rates between 78 and 113 cases per 100,000 people.

Eight counties have not yet reported any instances of whooping cough. In King County, there are about 6.5 cases per 100,000.

Whooping cough often begins with common cold symptoms, including a runny nose, but can lead to severe coughing fits that can last for weeks or months, according to DOH. Babies are at the highest risk for severe illness and death. Some infants might not show typical coughing symptoms, but can experience "dangerous pauses" in their breathing, DOH said.

"To protect babies from whooping cough, people of all ages should get up to date on pertussis vaccination, and anyone with symptoms should see a health care provider to see if testing and antibiotic treatment are needed," Kwan-Gett said.

Whooping cough vaccines are the most effective way to prevent severe illness from the infection, according to local and national health experts.

The shots are routine and "extraordinarily safe," Dr. Helen Chu and Collrane Frivold, infectious disease and vaccine researchers at the University of Washington, wrote in an op-ed published in The Seattle Times this week.

"Unfortunately, skepticism that arose during the pandemic about the safety and efficacy of the COVID-19 vaccine has bled over into a declining confidence in routine childhood vaccines, and now many children, teens and young adults in our community are under-vaccinated," Chu and Frivold wrote.

In Washington, the rate of K-12 childhood immunizations has settled at around 90% the past few school years — lower than it was during the worst of the pandemic, but higher than before 2020. Public health officials have been particularly concerned about kindergartners, who have reported lower vaccination rates the past two years. During the 2023-2024 school year, about 87% of them were up-to-date on immunizations, compared with about 91% during the 2020-2021 year, state data shows.

Lower vaccination rates mean "we can expect to see outbreaks of several vaccine-preventable diseases like measles and whooping cough now that schools are back in session," Chu and Frivold said in the op-ed.

In late August, Clark County's public health department warned its residents about the continued rise in whooping cough cases there. About 65% of people who got sick had never received a whooping cough vaccine, according to Clark County public health.

In the U.S., the whooping cough vaccine comes in two forms: DTaP and Tdap, which both also help protect against tetanus and diphtheria, according to the Centers for Disease Control and Prevention. While the shots work well, protection decreases over time, the CDC says.

Waning immunity ultimately accounted for many of the cases seen in the state's whooping cough epidemic of 2012, Chu and Frivold wrote. That year, The Seattle Times reported the state had the third-highest rate of whooping cough cases in the nation and almost 5,000 infections. The outbreak prompted dozens of federal disease investigators to descend on the state, in addition to others with high infection rates, to figure out what was behind the wave of cases.

Another significant whooping cough outbreak hit the state in 2015, when we had about 1,380 cases, according to DOH.

"There's now a recommendation for a (pertussis vaccine) booster dose in adolescents to prevent this waning immunity," Chu said during a UW Medicine news conference last month.

Pregnant people are encouraged to get the Tdap vaccine between 27 and 36 weeks of pregnancy, which helps protect their babies after birth, until they're old enough to start the whooping cough vaccination series at two months old.

State health officials are "closely monitoring" the continued spread of whooping cough and are working with local health teams to provide resources and support, DOH said.

For more information about whooping cough or what to do if you get sick, visit the state Department of Health website.

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