Global and Vietnam Epidemiological Situation

Global situation

Pertussis (Whooping Cough) is a common disease worldwide, especially in children. Before the introduction of vaccines, outbreaks occurred every 3–4 years in many countries. Thanks to vaccination and improved living conditions, the incidence decreased significantly (by 100–150 times) by 1970.

However, during the 1980s–1990s, the number of cases began to rise again. Specifically, from 1992 to 1994, up to 15,286 cases were reported, with a mortality rate of 0.2%. Notably, 50% of these cases had not been vaccinated. Epidemiological studies also indicate that the actual number of cases is much higher than reported, and the protective effect of the whole-cell pertussis vaccine may decline rapidly over time.

In some countries such as the United Kingdom and Sweden, the incidence has increased again due to a decline in vaccination coverage.

Situation in Vietnam

Pertussis is widespread throughout Vietnam. Before the Expanded Program on Immunization (EPI), the disease frequently caused outbreaks due to its high transmissibility. During epidemics, the disease was severe and associated with a high mortality rate, especially in children under 5 years old and malnourished children, who are more susceptible to complications such as pneumonia or bronchopneumonia.

Causative agent

The causative agent is Bordetella pertussis, which causes disease in humans. The bacterium is killed within one hour by heat, direct sunlight, or common disinfectants.

Immunosuppression and smoking are also considered factors that worsen pertussis symptoms and increase hospitalization rates. In patients with pre-existing asthma or chronic obstructive pulmonary disease (COPD), symptoms tend to be more severe.

Clinical manifestations

The disease may begin with no fever or mild fever, upper respiratory catarrh, fatigue, loss of appetite, and cough. The cough gradually worsens and develops into paroxysmal coughing within 1–2 weeks, lasting 1–2 months or longer. The coughing fits are characteristic: the child coughs violently and uncontrollably, followed by a high-pitched “whoop” sound during inhalation. At the end of each coughing episode, a large amount of clear sputum is produced, often followed by vomiting. After each episode, the child appears exhausted, sweaty, and breathes rapidly. Apnea may occur in young children.

Mode of transmission

Transmission occurs through direct respiratory contact with secretions from the nose and throat of infected patients during coughing or sneezing. The disease is highly contagious shortly after exposure to infected droplets, especially among people living in enclosed environments for long periods such as households and schools. The infection rate among household contacts is 90-100%.

Complications

Common complications in young children include bronchitis, bronchopneumonia due to secondary infection, prolonged coughing, and apnea (temporary pause in breathing), which is the most frequent and potentially fatal complication, especially in children under 1 year of age.

Other possible complications include intussusception, hernia, and rectal prolapse. Severe cases may develop alveolar rupture, pneumomediastinum, or pneumothorax. Encephalitis (0.1%) is a serious complication with high rates of mortality and long-term sequelae.

Prevention of pertussis

Vaccination remains the most effective and proactive preventive measure. Several combination vaccines can protect against pertussis:

  • Infanrix Hexa (pertussis, diphtheria, tetanus, polio, hepatitis B, and Haemophilus influenzae type b – Hib)
  • Hexaxim (pertussis, diphtheria, tetanus, polio, hepatitis B, Hib)
  • Pentaxim (pertussis, diphtheria, tetanus, polio, Hib)
  • ComBe Five (pertussis, diphtheria, tetanus, hepatitis B, Hib)
  • Tetraxim (pertussis, diphtheria, tetanus, polio)
  • Adacel (pertussis, diphtheria, tetanus)
  • Boostrix (pertussis, diphtheria, tetanus)
  • DPT (pertussis, diphtheria, tetanus)
  • Tdap (pertussis, diphtheria, tetanus)

Homes, daycare centers, and classrooms should be well ventilated, clean, and adequately lit.

In areas with previous pertussis outbreaks, surveillance should be strengthened to detect early cases with typical coughing fits, especially during the expected epidemic cycle.

Important notes

  • Booster vaccination is recommended for preschool children (4–7 years old) and then every 10 years thereafter.
  • Pregnant women should receive one dose of Tdap between weeks 27–36 of pregnancy to protect newborns from pertussis from birth.
  • Vaccination is recommended for individuals with underlying conditions such as asthma, COPD, or obesity, as they have a higher risk of infection or severe exacerbations.