Whooping cough outbreak sparks push for testing, vaccination

Amid statewide outbreaks of pertussis (also known as whooping cough), three Eden Prairie Schools sites and one school sports team recently sent community alerts warning students and their families about identified cases.

Eden Prairie High School (EPHS), Central Middle School, Eagle Heights Spanish Immersion, and the EPHS Nordic Ski team all received alerts last week. The EPHS community also received an alert in December.

Eden Prairie is not alone in experiencing high levels of pertussis cases. There are currently 24 active school outbreaks across eight counties, according to the Minnesota Department of Health (MDH). Many other schools have been impacted over the past year. MDH considers a school to have an outbreak when two or more cases are reported. 

While case rates across the state have generally trended downward this month, they surged in October and November to their highest levels since 2012, with a preliminary estimate of 3,268 cases.

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Pertussis is a bacterial illness that typically begins with a runny nose, sneezing, mild cough, and possibly a low-grade fever. However, it can quickly become more serious and lead to dangerous respiratory distress.

After one to two weeks, the cough worsens and occurs in sudden, uncontrollable bursts. These coughing attacks can lead to vomiting or a high-pitched whooping sound, though older children and adults may have a milder form of the illness. Some may not develop the characteristic “whoop” but instead experience a persistent cough. Coughing attacks often occur at night and can last up to three months.

Being vaccinated against pertussis does not guarantee immunity, as the vaccine’s effectiveness wanes over time. This helps explain why so many teenagers are contracting it – the average age of Minnesota cases in 2024 was 14. However, being fully vaccinated has been shown to reduce the severity of symptoms, especially in high-risk populations such as children under age 1.

Danielle Ryan, a public information officer at MDH, said individuals should be evaluated for pertussis if they have a persistent cough lasting more than seven days. “We also recommend that anyone who has had close contact to someone with pertussis be tested even earlier if they develop a cough,” she said.
 

It is important to know that pertussis is highly contagious. People with pertussis should not go to school, work, or any activities until they have finished five days of antibiotic treatment. The exception is if they have already been coughing for three or more weeks, at which point they are no longer contagious.

Why cases spike – and how vaccination helps

Reported pertussis cases have gradually increased in the United States since the late 1980s and early 1990s, with large spikes observed since the mid-2000s. These spikes occur every three to five years. Confirmed case statistics by year are available on the Minnesota Department of Health website.

There are several reasons Minnesota has seen more pertussis cases recently, Ryan said:

• The natural three- to five-year cycle of pertussis peaks was disrupted during the COVID-19 pandemic, leading to a larger peak this past year.
• With more pertussis circulating, people are more aware of the disease and better at recognizing and identifying cases.
• Vaccine-induced immunity wanes over time. 

Vaccination remains the most effective way to reduce the risk of contracting pertussis, Ryan said. She noted that while Minnesota has not seen a big change in pertussis vaccination rates lately, “with only 78% of children and adolescents receiving their pertussis-containing vaccines, there is still room for improving and increasing our rates.”

Two vaccines protect against pertussis, and the one a person receives depends on their age. Children under 7 get the DTaP vaccine, while adolescents and adults receive Tdap.

DTaP vaccine

• The MDH estimates that about 78% of children who turned 6 to 8 years old in 2024 (born in 2016-2018) have received a complete DTaP series.
• Studies show that in children who get all five doses of DTaP on schedule, the vaccine is 98% effective at protecting against pertussis in the first year following their last dose.
• Vaccine effectiveness then decreases to about 71% five years after getting their last DTaP. When pertussis is circulating widely in the community, some cases occur in these younger age groups. 

Tdap vaccine

• About 78% of adolescents who turned 13 to 15 years old in 2024 (born in 2009-2011) have received at least one dose of Tdap.   
• After receiving Tdap at age 11 or 12, most Minnesotans are not recommended to receive another Td or Tdap for 10 years.  
• Studies show that the Tdap vaccine is about 73% effective at preventing pertussis in the first year after vaccination. Effectiveness then declines to about 34% at four years after receiving the vaccine.

Vaccination is also recommended during pregnancy. Studies by the Centers for Disease Control and Prevention show:

• The vaccine is about 78% effective at preventing pertussis in infants younger than 2 months old
• The vaccine is about 90% effective at preventing hospitalizations due to pertussis in infants younger than two months. 

It’s important for pregnant women to receive the Tdap vaccine during pregnancy to help protect their baby by passing on antibodies, as infants are at high risk for severe pertussis symptoms in their first year of life, Ryan said.

While vaccine effectiveness wanes over time, it is still the best tool to prevent severe illness and deaths from pertussis. 

To learn more, visit the MDH website or contact a medical provider.