Whooping cough has a reputation as a Victorian disease consigned to history by vaccination. In reality, it resurfaces with predictable cyclicality — the 2024 UK outbreak was the largest in over thirty years. The bacteria have not disappeared; herd immunity through vaccination has simply reduced their circulation to the point where most people never encounter them. When vaccination rates fall or when the immunity gap widens, they come back.
The distinctive sound of whooping cough — an extended, exhausting coughing fit that ends with a desperate, high-pitched intake of breath — is one of the more distressing things to witness in a child. In a young infant, the whoop may never appear; instead, there is a silent, frightening episode where the infant stops breathing, turns blue, and takes a long moment to restart. This is the version that kills.
Healthbooq (healthbooq.com) covers infectious diseases and vaccination in children.
The Illness
Whooping cough has three phases. The catarrhal phase (one to two weeks) resembles an ordinary cold: runny nose, mild cough, low fever. This is when the child is most infectious. Most cases at this stage are not recognised as whooping cough.
The paroxysmal phase (two to ten weeks) is when the characteristic coughing begins. Paroxysms are sudden, repeated bursts of coughing within a single expiration, until all air is expelled. The whoop occurs when the child finally gasps in air against a partially narrowed glottis. Coughing fits can be triggered by eating, drinking, crying, or nothing in particular. Posttussive vomiting (vomiting after a coughing fit) is common. Between paroxysms the child may appear completely well.
The convalescent phase involves gradual improvement over weeks. Coughing fits may recur with subsequent respiratory infections for many months — hence the Chinese name for the illness, "the hundred-day cough."
Why Infants Are Most at Risk
In infants under three months — before the primary course of vaccination can be completed — whooping cough can be life-threatening. The coughing fits are so exhausting and sustained that infants can develop hypoxia. Younger infants may have apnoeas rather than whoops. Complications include pneumonia, encephalopathy, and death. Worldwide, pertussis kills an estimated 200,000 to 300,000 people per year, the majority of them infants in low-income settings.
In the UK, the most vulnerable period is the first few weeks of life before the first diphtheria-tetanus-pertussis (DTP) vaccine at eight weeks.
Vaccination and Maternal Immunisation
The UK childhood immunisation schedule includes pertussis as part of the 6-in-1 vaccine (containing DTP, Hib, hepatitis B, and polio) at eight, twelve, and sixteen weeks, with boosters at three to four years. Immunisation reduces the severity and duration of illness even if it does not completely prevent infection — vaccinated children who contract whooping cough have significantly milder disease.
Maternal pertussis vaccination (as part of the Tdap vaccine, offered from 16 weeks of pregnancy) provides passive protection to newborns via maternal antibodies transferred across the placenta. This is the single most effective intervention for protecting newborns before they can receive their own vaccines. Uptake of maternal vaccination in the UK fell during the COVID-19 pandemic, contributing to the increased infant vulnerability during subsequent outbreaks.
Diagnosis
Clinical diagnosis can be made on the basis of the characteristic paroxysmal cough lasting more than two weeks with the whoop or posttussive vomiting. Laboratory confirmation uses nasopharyngeal swab PCR (polymerase chain reaction) for Bordetella pertussis, which is most sensitive in the catarrhal and early paroxysmal phases. Serology (pertussis antibodies) is used in later illness.
Treatment
Azithromycin (or clarithromycin) given within the first three weeks of illness reduces the infectious period and may slightly reduce severity. After three weeks, antibiotic treatment does not alter the clinical course but may be given to reduce ongoing transmission.
Household contacts of a confirmed case should receive prophylactic azithromycin, particularly if there are unvaccinated infants in the household.
Infants under six months with suspected pertussis and any infant with apnoeas, cyanosis, or difficulty feeding should be admitted to hospital for monitoring and supportive care.
Key Takeaways
Whooping cough (pertussis) is caused by Bordetella pertussis, a highly contagious bacterial infection that causes paroxysmal coughing fits followed by the characteristic 'whoop' — a high-pitched inspiratory gasp. It is most severe and most dangerous in infants under three months, who may not produce a whoop at all but instead have apnoeas (breathing pauses), cyanosis, and posttussive vomiting. Vaccination is the primary prevention strategy; maternal pertussis vaccination in pregnancy (from 16 weeks) protects newborns before they can receive their own vaccines. The UK has experienced periodic outbreaks including a significant one in 2024. Azithromycin given early in the illness reduces the infectious period.
