Acellular pertussis

Pertussis, commonly known as whooping cough, is a highly contagious respiratory disease caused by the bacterium Bordetella pertussis. While this illness can affect people of all ages, it is particularly dangerous for infants and young children. The acellular pertussis vaccine (aP) has been developed to protect against this illness, replacing the older whole-cell vaccine in many parts of the world due to its improved safety profile.

In recent decades, pertussis has seen a resurgence in several countries, including India. This makes vaccination and awareness crucial. This article explores all aspects of acellular pertussis—from the disease it prevents to how it impacts public health, especially in India and globally.

Acellular pertussis refers to the pertussis component of combination vaccines (like DTaP and Tdap) that use purified antigens instead of the whole bacterium. These antigens are carefully selected to stimulate immunity while minimising adverse reactions.

The acellular vaccine targets toxins and proteins produced by Bordetella pertussis that cause illness. It differs from the whole-cell vaccine, which contained inactivated bacteria and was associated with higher rates of side effects like fever and swelling.

India

In India, pertussis remains a significant public health issue, especially in rural and underserved regions. According to WHO and UNICEF, India reported over 10,000 cases in recent years, though underreporting may mean the actual number is higher.

Worldwide

Globally, the World Health Organization (WHO) estimates 24.1 million pertussis cases and 160,700 deaths in children under five annually (as of 2020), most of which occur in developing countries.

While acellular pertussis itself is a type of vaccine, pertussis illness presents in different clinical forms:

• Typical Pertussis: Characterised by severe coughing fits followed by a "whoop" sound.
• Atypical Pertussis: Seen more in vaccinated individuals—less severe and may resemble bronchitis.
• Pertussis in Infants: May lack the typical cough but show signs like apnoea or poor feeding.

Pertussis infection is caused by Bordetella pertussis, a bacterium that attaches to the lining of the respiratory tract. It releases toxins that damage the respiratory epithelium and impair the body’s immune response.

Risk of infection increases due to:

• Lack of vaccination or incomplete immunisation
• Waning immunity (especially in adolescents and adults)
• Close contact with infected individuals
• Outbreaks in communities with low vaccine coverage

Pertussis develops in three stages:

1. Catarrhal Stage (1–2 weeks)

• Runny nose
• Sneezing
• Mild cough
• Low-grade fever

2. Paroxysmal Stage (1–6 weeks)

• Severe coughing spells
• "Whooping" sound when inhaling
• Vomiting after coughing
• Exhaustion

3. Convalescent Stage (weeks to months)

• Gradual recovery
• Decreasing cough severity

In infants, symptoms may be subtle but life-threatening, such as apnoea, cyanosis, or seizures.

Early diagnosis is essential for effective treatment and limiting spread.

Common diagnostic methods include:

• Nasopharyngeal Swab for PCR or Culture: Detects the bacteria directly.
• Serology: Measures antibodies against pertussis toxins.
• Complete Blood Count (CBC): May show elevated white blood cell count.

Timely treatment helps reduce severity and spread.

Medications

• Antibiotics: Azithromycin, clarithromycin, or erythromycin—effective in early stages.
• Supportive Care: Oxygen therapy, intravenous fluids, and monitoring in severe cases, especially for infants.
• Antitussives: Not usually effective and not recommended.

Hospitalisation

Infants, especially those under 6 months, often require hospital care due to risk of complications like pneumonia or seizures.

Vaccination

Vaccines like DTaP (children) and Tdap (adolescents and adults) are the primary preventive measures. (Prevenar 13 vaccine)

There is limited evidence for alternative therapies, but some supportive approaches include:

• Honey for older children and adults: Can soothe coughs.
• Steam inhalation: May ease breathing.
• Probiotics: To restore gut flora if antibiotics are used.

Note: These do not replace conventional treatment.

• Unvaccinated individuals
• Infants under 1 year
• Pregnant women not receiving Tdap
• Healthcare workers
• People with chronic lung conditions

• Pneumonia
• Seizures
• Encephalopathy
• Apnoea (in infants)
• Rib fractures (from intense coughing)
• Weight loss and dehydration

These complications underscore the importance of vaccination.

• Stay Hydrated: Coughing can lead to dehydration.
• Eat Soft Foods: Reduces cough-triggering.
• Get Plenty of Rest: Speeds up recovery.
• Use a Humidifier: Eases breathing.
• Limit Physical Activity: Until coughing improves.

For vaccinated individuals, maintain booster schedules to prevent reinfection.

• "Vaccinated people can't get pertussis": Vaccination reduces severity but doesn’t offer lifelong immunity.
• "It only affects children": Adults and adolescents can get and spread pertussis.
• "Natural infection is better than vaccination": Infection can cause severe complications.
• "Antibiotics cure all symptoms": They only prevent transmission and are most effective early on.

• Persistent, severe cough lasting over a week
• Breathing difficulties or choking during coughing
• Vomiting after coughing
• Cyanosis (bluish lips or face)
• High fever in children or infants

Early intervention can prevent serious outcomes
 

• Should I or my child receive a pertussis booster?
• Are there side effects to the aP vaccine?
• What precautions should I take if someone in my home has pertussis?
• How long is the illness contagious?
• What signs indicate an emergency in infants?

• Provide a calm, quiet environment
• Offer fluids frequently
• Keep airways clear
• Encourage rest and minimise stres
• Monitor symptoms for worsening
• Help them follow medication schedule

Support can make recovery less stressful, especially for children.

Acellular pertussis vaccines have significantly improved the safety and effectiveness of pertussis prevention. While pertussis remains a public health challenge in both India and globally, adherence to immunisation schedules and prompt medical care can mitigate its impact. With rising awareness, continued research, and timely vaccinations, the burden of this disease can be drastically reduced.