Introduction
Pertussis (also known as whooping cough) is a bacterial lung infection that can cause intense coughing and shortness of breath, leading to a characteristic “whooping” sound that lends the disease its name.1 Infants less than one year of age are at greatest risk of severe and life-threatening complications. Although pertussis vaccines are available to mitigate this risk, rates of pertussis have been on the rise in several parts of the world, including the United States and the European Union.2 As young infants aren’t yet fully vaccinated and have less robust immune systems, they are at particular risk from pertussis and suffer the highest mortality rates due to this highly infectious disease. Read on to discover the connection between pertussis and infant mortality.
Understanding pertussis
Pertussis is a very contagious infection of the lungs caused by the bacteria, Bordetella pertussis, which attacks the tiny hairs that line the lungs and release toxins that damage the airways.3 The bacteria is transmitted through droplets in the air released by an infected person’s cough or sneeze. An infected person can be contagious for a long period of time starting when symptoms first present themselves and lasting for 2 or more weeks after the cough begins.3 It is easy for those who don’t know they have pertussis, or who think they may only have a mild cold, to pass the infection to others. Infants with pertussis often get it from the older children or adults around them.
Symptoms typically begin 5-10 days after exposure to pertussis and usually start as mild, cold-like symptoms.4 A mild cough, runny nose, or fever may last for a week or two. However, symptoms in infants may look different - they may cough only a little or not at all, and may instead have apnea. Apnea is a pause in breathing, which may cause their lips to turn blue and may make it difficult for them to breathe.3 Some babies may only have mild symptoms for a week or two. As the disease progresses, some may start having intense coughing fits, known as paroxysms, that can last for another 1 to 10 weeks.3 These intense coughing fits can cause a high-pitched “whooping” sound or can cause the infected person to vomit, feel exhausted, have a hard time breathing, and have trouble sleeping.3 The path to recovery can be slow as symptoms gradually improve.
The most common complication of pertussis is pneumonia, which is the cause of most deaths attributed to pertussis.4 Young infants are at the highest risk of developing complications, which may also include seizures and brain swelling from lack of oxygen to the brain.
Pertussis is diagnosed by a medical provider by taking a history of symptoms, a physical exam, and perhaps other tests such as a sample of mucous from the back of the throat, and other tools like a blood test or chest x-ray.5 Treatment consists of antibiotics, which are most effective if given early in the course of the disease. Antibiotics may help reduce the severity of the illness and could reduce the spread of the infection to others. However, starting treatment after 3 weeks of symptoms is less effective, which is why early treatment is so important.5 Babies under 1 year of age are at highest risk of complications. They may require hospital care to monitor their breathing, oxygen levels, and hydration status.
The impact of pertussis on infant mortality
According to the World Health Organization, more than 240 million children under age 5 are affected by pertussis each year, with a mortality rate of 4%.6 Other studies have shown that children and infants who develop severe pertussis suffer high rates of mortality, ranging from 10.7%-31%.7 Infants, in particular, suffer the highest rates of mortality, with one study showing a mortality rate of 70% among infants with severe pertussis.6
Infant mortality refers to the death of a baby before one year of age. Infant mortality related to pertussis is most likely to occur in the youngest babies. Research from various countries has consistently shown that the majority of hospitalisations and deaths due to pertussis occur in infants less than 6 months of age.8 Infants less than 3 months of age are at the highest risk for severe disease and death.11 According to the Centers for Disease Control and Prevention (CDC), children under the age of 2 months accounted for 84% of all pertussis-related deaths that occurred between 2000 to 2017.4 These children are too young to have completed the vaccine series, which typically begins at 2-3 months of age and requires a total of 3 shots.
Because of their young age, infants have an immature immune system and cannot fight the vaccine in the same way that adults can. Additional risk factors for pertussis death in this population include prematurity, lower birth weight, and female sex.9 Infants infected with pertussis who develop severe apnea, a high white blood cell count, or pulmonary hypertension, which is a condition that causes high blood pressure in the lungs, have a greater risk of death.9 Infants with pre-existing medical conditions are also at a higher risk of severe disease and death from pertussis.
Vaccination and prevention
The most effective way to prevent pertussis and protect infants is to get vaccinated. There are two types of vaccines available - one for children younger than 7 years old (DTaP) and one for older children, adults, and pregnant women (Tdap). Studies have shown that DTaP fully protects almost all children (98 out of 100) in the year after vaccination, and fully protects the majority of children (7 out of 10) five years after the last dose.3 Very young babies who are too young to receive the vaccination or haven’t yet finished getting all the vaccines in the series are among those at the highest risk of suffering severe complications from pertussis. The CDC states that about one-third of infants with pertussis end up hospitalised.7 That’s why it is so important for older children and adults to get vaccinated. As a bonus, those who are vaccinated typically have milder symptoms and shorter course if they end up catching pertussis.
Across the globe, pertussis is still one of the leading causes of vaccine-preventable deaths. The first vaccine for pertussis became available in the 1940s, and the incidence of pertussis has decreased by more than 75% since the vaccines became widely available.4 However, rates have increased since the 1980s, likely due to improved diagnosis of pertussis by healthcare professionals, better access to laboratory tests to help identify pertussis, improved tracking of the disease by public health departments, and waning immunity from vaccines.10
Vaccination of pregnant women against pertussis began in 2011, and studies show that the rates of pertussis have significantly decreased since then.11 The vaccination during pregnancy provides protection until the newborn is old enough to get the vaccine. Unfortunately, the CDC reports that only half of pregnant women get the vaccine.11 In developing countries, the incidence of pertussis is highest among babies who have not been vaccinated.
Conclusion
Pertussis is a common bacterial respiratory infection that can cause severe symptoms, particularly in infants. Young infants, in particular, are at greatest risk for severe disease and death caused by pertussis. Widespread use of the pertussis vaccine led to a significant decrease in pertussis incidence and mortality. Annual rates of pertussis vary greatly by country, which may be due to factors like vaccination rates, diagnostic procedures, reporting methods, and greater disease awareness. To protect the youngest and most vulnerable members of society from the disease, higher vaccination rates are needed. More vaccination of adults, older children, and pregnant women will confer indirect protection to vulnerable infants.
References
- HealthyChildren.org [Internet]. [cited 2024 Jun 7]. Whooping cough (Pertussis): what parents need to know. Available from: https://www.healthychildren.org/English/health-issues/conditions/chest-lungs/Pages/Whooping-Cough.aspx
- Increase of pertussis cases in the EU/EEA [Internet]. 2024 [cited 2024 Jun 7]. Available from: https://www.ecdc.europa.eu/en/publications-data/increase-pertussis-cases-eueea
- CDC. Pertussis (Whooping Cough). 2024 [cited 2024 Jun 7]. About whooping cough. Available from: https://www.cdc.gov/pertussis/about/index.html
- Pinkbook: pertussis | cdc [Internet]. 2022 [cited 2024 Jun 7]. Available from: https://www.cdc.gov/vaccines/pubs/pinkbook/pert.html
- Whooping cough [Internet]. [cited 2024 Jun 7]. Available from: https://medlineplus.gov/whoopingcough.html
- Shi T, Wang L, Du S, Fan H, Yu M, Ding T, et al. Mortality risk factors among hospitalized children with severe pertussis. BMC Infectious Diseases [Internet]. 2021 Oct 12 [cited 2024 Jun 8];21(1):1057. Available from: https://doi.org/10.1186/s12879-021-06732-1
- CDC. Pertussis (Whooping Cough). 2024 [cited 2024 Jun 7]. Symptoms of whooping cough. Available from: https://www.cdc.gov/pertussis/signs-symptoms/index.html
- Burr JS, Jenkins TL, Harrison R, Meert K, Anand KJS, Berger JT, et al. The collaborative pediatric critical care research network (Cpccrn) critical pertussis study: collaborative research in pediatric critical care medicine. Pediatr Crit Care Med [Internet]. 2011 Jul [cited 2024 Jun 8];12(4):387–92. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3439849/
- Liu C, Yang L, Cheng Y, Xu H, Xu F. Risk factors associated with death in infants <120 days old with severe pertussis: a case-control study. BMC Infectious Diseases [Internet]. 2020 Nov 16 [cited 2024 Jun 8];20(1):852. Available from: https://doi.org/10.1186/s12879-020-05535-0
- CDC. Whooping Cough (Pertussis). 2024 [cited 2024 Jun 7]. Pertussis surveillance and trends. Available from: https://www.cdc.gov/pertussis/php/surveillance/index.html
- Jenco M. Study: Tdap vaccination during pregnancy linked to lower pertussis rates in newborns. 2023 Feb [cited 2024 Jun 7]. Available from: https://publications.aap.org/aapnews/news/23521/Study-Tdap-vaccination-during-pregnancy-linked-to