By Philip R. Fischer, MD, DTM&H
Synopsis: Related to under-immunization of pregnant women and children, pertussis is spreading in several countries within the Americas. Macrolide resistance of Bordetella pertussis is now common in China.
Source: Silva Dirzo M, Castillo Bejarano JI, Casillas Casillas MC, et al. Unraveling the pertussis outbreak in Mexico: Insights from a multi-center 2024-2025 study. Pediatr Infect Dis J. 2025; Sep 10. doi: 10.1097/INF.0000000000004986. [Online ahead of print].
In Latin America, the incidence of pertussis rose during and after the COVID-19 pandemic. Several countries reported three- to four-fold increases in the number of reported pertussis cases. In Mexico, a national public health alert was issued in May 2025 as cases rose to 0.73 per 100,000 residents; the case fatality rate was 5%, with deaths spread over 17 states. Most deaths were in unimmunized infants younger than 6 months of age.
With that background, an investigative team reviewed demographic and clinical features of pediatric patients diagnosed to have pertussis in Mexico during the 2024-2025 outbreak. Fifteen children’s hospitals spread throughout Mexico provided information about 59 patients younger than 18 years of age who had polymerase chain reaction (PCR)-confirmed pertussis. The median age of affected children was 4 months; 59% of subjects were younger than 6 months of age. Males represented 51% of the children in the study. Half of patients were admitted during January through March.
Only 27% of mothers of infected children had received the recommended dose of Tdap (acellular pertussis with tetanus and diphtheria) vaccine during pregnancy. Just 10% of patients had received even an initial pertussis vaccine. Among mothers, 31% had symptoms consistent with pertussis.
Nine infected children were hospitalized prior to 2 months of age, the time at which the initial pertussis vaccine could have been given. One of those patients died. Neither of the two youngest patients whose mothers had received Tdap during pregnancy died.
Approximately 90% of these hospitalized children with pertussis presented with respiratory distress and paroxysmal cough; about 80% were cyanotic during coughing spells. Post-tussive emesis was seen in 28% of patients, apnea in 10%, and seizures in 5%.
Overall, 14% of patients died. The one patient with concurrent coronavirus infection died. Other risk factors for death included higher leukocyte counts and having a symptomatic mother. The authors of this study suggest increasing maternal immunization to reduce the risk of pertussis in infants. They also advocate for earlier diagnosis and treatment to reduce fatal outcomes.
Commentary
The recently reported Mexican experience represents tragedy for the families and communities of the 59 hospitalized children with pertussis (and especially for the families and communities of the eight of those children who died). Nonetheless, this study only included children sick enough to be hospitalized in settings where confirmatory PCR testing was done. Thus, these data likely represent a mere “tip of the iceberg,” with pertussis affecting many, many more people in Mexico and prompting calls for improved public health intervention.
In Brazil during 2024, the incidence of documented pertussis rose 34-fold as compared to 2023.1 For the first time in three years, there were reported deaths due to pertussis (none in 2021, 2022, and 2023; 30 in 2024).1 Reductions in the incidence of pertussis during the COVID-19 pandemic have been reversed, with rates now the highest during the past 10 years.1 Although much of the increase is in children, older adolescents and adults are demonstrating increasing rates of pertussis as well.1
In the United States, reflecting in part the recent Brazilian experience, the incidence of pertussis dropped to very low levels during the 1960s and then rose to peaks in 2003, 2013, and 2024.2 In the United States, incidence rates are two- to four-fold higher in infants than in older children and adolescents.2 The rising rates of pertussis in the Americas demonstrate the opportunity for beneficial effects of improving vaccination coverage with pertussis vaccines, not just for children but also for pregnant women, adolescents, and adults. In fact, the Centers for Disease Control and Prevention recommends pertussis vaccine for everyone: five doses of DTaP before age 6 years, a dose of Tdap at age 11-12 years, a dose of Tdap between the 27th and 36th weeks of each pregnancy, and a single dose of Tdap for any adult who has not yet received a Tdap vaccine.3
Similarly, the incidence rates of pertussis have been surging in China since early 2023.4 In a recent Chinese study, 47 of 48 cultured Bordetella pertussis samples carried a genetic marker for macrolide resistance.4 It remains to be seen if macrolide-resistant pertussis will spread to the Americas as well.
Meanwhile, there is good news as well as unmet opportunity in the United States. The coverage of adolescents by the Tdap vaccine increased from 89% in 2023 to 91% in 2024.5 Still, though, the coverage of pregnant women with Tdap is a bit more spotty; in 2020-2022, 68% of privately insured pregnant women and 41% of publicly insured pregnant women received pertussis vaccine.6
Philip R. Fischer, MD, DTM&H, is Professor of Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN.
References
- Sansone NMS, Boschiero MN, Marson FAL. The 2024 resurgence of Bordetella pertussis in Brazil and a decade-long epidemiological overview. Front Public Health. 2025;13:1549735.
- Parikh J, Hoare I, Izurieta R. Evaluating the relationship between the introduction of the acellular pertussis vaccine and whooping cough resurgence in the United States. Vaccines (Basel). 2025;13(8):841.
- Centers for Disease Control and Prevention. Whooping cough vaccination. June 26, 2024. www.cdc.gov/pertussis/vaccines/index.html
- Qin S, Wang Z, Wu Y, et al. High prevalence of macrolide-resistant ptxP3-prn150 Bordetella pertussis in Jiangsu Province, China, 2024. Pediatr Infect Dis J. 2025; Sep 5. doi: 10.1097/INF.0000000000004963. [Online ahead of print].
- Pingali C, Yankey D, Elam-Evans LD, et al. Vaccination coverage among adolescents aged 13-17 years — National Immunization Survey — Teen, United States, 2024. MMWR Morb Mortal Wkly Rep. 2025;74(30):466-472.
- Rowe SL, Sullivan SG, Munoz FM, et al. Uptake of recommended vaccines during pregnancy among publicly and privately insured people in the United States, December 2020-September 2022. Am J Public Health. 2025;115(3):354-363.
Related to under-immunization of pregnant women and children, pertussis is spreading in several countries within the Americas. Macrolide resistance of Bordetella pertussis is now common in China.
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