Marin whooping cough cases level off after spike

A nearly yearlong surge in whooping cough cases in Marin appears to be winding down while outbreaks are ramping up in other areas of the state.

“Unlike other counties, we’re seeing a downshifting in the number of cases,” said Dr. Lisa Santora, Marin County’s public health officer.

News outlets have reported a significant rise statewide in the number of whooping cough cases. Department of Public Health data showed 1,744 cases statewide this year through Sept. 30, up from 644 cases during the entire previous year.

Despite its relatively small population, Marin had 336 cases by the end of September, according to the data. The only county to report more was San Diego, with 470.

Santora said Marin actually confirmed 355 whooping cough cases by Sept. 30, but has only identified 14 cases since then.

Whooping cough, also known as pertussis, is a highly contagious respiratory illness. Initial symptoms, which include fever, a runny nose and a cough, usually resemble a common cold, but they can quickly progress to violent coughing. A characteristic “whooping” sound is heard when sufferers inhale from the coughing.

Adolescents and adults typically recover without complications or treatment, but the illness can be deadly for infants. Santora said none of the Marin residents who became infected needed to be hospitalized.

California mandates that children enrolling in transitional kindergarten and kindergarten receive a vaccination for pertussis, diphtheria and tetanus. State law also requires students to get another round when starting seventh grade. Santora said that often adolescents contract whooping cough in high school after their immunity has had time to wane.

Marin’s surge of whooping cough cases began in December, primarily among adolescents. By March 22, the county’s communicable disease unit had investigated 77 cases, including 52 connected to an outbreak at Tamalpais High School. By the end of the month, another 13 cases had been identified at the school.

Whooping cough typically spreads through droplets when infected people cough.

“Masking is a great tool to reduce transmission,” Santora said.

Nevertheless, Tara Taupier, superintendent of the Tamalpais Union High School District, said at the time of the outbreak that masks were not mandated.

Santora said that while the number of whooping cough cases in Marin this year has been high, surges of this kind are not unprecedented. During the 2018-19 winter, the county had nearly 300 cases.

Santora said spikes in the number of whooping cough cases occur at regular intervals, typically every three to four years. She said the surges seem to coincide with the amount of time it takes for the immunity of children vaccinated in the seventh grade to begin to fade.

The recent uptick in whooping cough cases statewide has led to speculation that it might be linked to a decline in vaccinations during the COVID-19 pandemic, especially among young children.

More than a decade ago, Marin County’s childhood vaccination rates were among the lowest in the state. But the advent of tough new state laws mandating vaccinations and messaging efforts by the county to promote vaccinations have altered that picture.

Santora said that in 2022-23 and 2023-24, 99% of Marin’s seventh-grade students received their vaccination boosters for pertussis, tetanus and diphtheria.

Santora said she is concerned, however, that if Robert Kennedy Jr., President-elect Donald Trump’s nominee for secretary of the Department of Health and Human Services, is appointed, that the burden of communicating public health risks will be shifted back to local jurisdictions.

She said Kennedy has touted the work of Andrew Wakefield, who published a fraudulent scientific paper in the Lancet medical journal linking the measles, mumps and rubella vaccine and autism. The Lancet retracted the paper. Wakefield was later struck off the medical register.

Nevertheless, Santora said, Wakefield’s paper helped fuel opposition to vaccines in Marin.

“It takes energy and time when local health jurisdictions have to address misinformation,” Santora said. “One of my primary concerns is that we’ll have to redirect resources to address misinformation.”