You have been suffering from episodes of irritating cough for weeks, and are not getting any better with the medicines prescribed by your doctor.
The older folks may suggest to you all sorts of reasons, eg you're drinking too much ice water, or you're not getting sufficient rest. Little does it cross your mind, or that of most people, that this is no normal cough. It could be pertussis, or more commonly known as whooping cough.
Pertussis in adults
Pertussis is a disease caused by the bacteria Bordetella pertussis. Contrary to what most people believe, whooping cough is not just a childhood disease; it can affect people of all ages.
According to the Centers for Disease Control and Prevention (CDC), there were 25,000 cases of pertussis in the US in 2004. Out of these, more than 8,000 occurred in adolescents, and more than 7,000 in adults.
What differentiates the disease in adolescents and adults from that in children is that symptoms are generally mild, and the classic "whoop" is rare in adult pertussis. This means that the diagnosis is rarely made.
In adolescents and adults, pertussis may just appear as a persistent dry cough that lasts for weeks or months, which doesn't respond well to common cough treatments. Although they will not experience life-threatening complications of the infection, the persistent coughing can have a tremendous impact on their quality of life, disturbing their sleep and affecting their productivity.
Because the classic symptoms of pertussis are not manifested in the older population, the disease often goes undetected, and therefore undertreated. Sometimes, it may also be misdiagnosed as other respiratory disorders, such as asthma or bronchitis.
Therefore, many adolescents and adults may unknowingly contract and pass on pertussis to those who are not immune against the disease.
It is most contagious in the first two weeks of the infection, during which B. pertussis can be easily spread through the air when the infected person coughs or sneezes.
This can pose a great threat to vulnerable populations - infants and young children who are not fully vaccinated or just partially vaccinated against pertussis.
In fact, adolescents and adults are often the reservoir of disease transmission to infants too young to be protected by vaccination.
In recent years, there are increasingly more pertussis cases reported in older children, adolescents, and adults. Also, studies have shown that new parents, especially mothers, are the source of infection in more than 50% of pertussis cases.
The young ones suffer
If pertussis is passed on to unprotected infants and young children, the consequences can be very critical; it may lead to severe health complications or even fatality.
The infection starts very much like a common cold, with a runny nose, sneezing, mild fever and occasional cough. Two weeks later, the disease progresses into severe coughing spells that end in the characteristic "whooping" sound as the child gasps to breathe.
The uncontrollable coughing spells in pertussis can be very dangerous for babies. It can lead to vomiting, or during a particularly bad coughing spell, young children may turn blue due to lack of oxygen.
In very bad cases, violent coughing can even lead to cracked ribs. Bleeding within the white of the eyes can occur with violent coughing.
The infection is most serious and dangerous in infants and children younger than two years, as they are at greater risk for complications, such as pneumonia. Almost all pertussis-related deaths occur in children younger than six months.
While this infectious disease is preventable through vaccination, sadly it remains as one of the world's leading causes of deaths among infants.
Protection against pertussis
Since the introduction of the pertussis vaccine in the 1940s, and following large-scale vaccination during the 1950s and 1960s, the incidence and death rates due to pertussis was dramatically reduced in the industrialised world.
Pertussis vaccine is given in combination with diphtheria and tetanus toxoid (DTP), and is usually given to an infant at two, three, and five months, plus a booster dose at 18 months to reinforce immunity.
In 2008, about 82% of all infants worldwide received three doses of pertussis vaccine under the WHO's Expanded Programme on Immunisation. It is estimated that about 687,000 deaths were averted because of this global vaccination initiative.
Unfortunately, there were still about 16 million cases of pertussis reported in different parts of the world, and the disease had caused about 195,000 deaths in young children.
In Malaysia, sporadic cases of non-fatal pertussis have also been reported in the past decade. In more recent years, eight cases were reported in 2005, 15 cases in 2007, and 39 in 2009, despite pertussis vaccine being routinely given to infants under the national immunisation schedule.
So why are there still significant rates of pertussis occurring worldwide? Didn't we all get our protection shots when we were still babies?
The immunity wanes
Unlike some other vaccines (eg chickenpox vaccine) that confer life-long immunity, the protection acquired from childhood pertussis vaccination is short-lived and incomplete.
The protective effect of the pertussis vaccine wanes over time, typically lasting for only four to 12 years. Despite completing the childhood immunisation, one may have already lost the immunity and become susceptible to the disease upon reaching adolescence.
When more and more people lose their protection against pertussis, this eventually creates a disease-vulnerable population. It could be an epidemic waiting to erupt. Revaccinating against pertussis with an additional booster dose is the most effective way to re-establish immunity amongst the population to reduce the incidence of the disease. A high level of community immunity also helps lower the risk of vulnerable infants and young children being exposed to pertussis.
Therefore, it is important for older children, adolescents and adults to receive periodic pertussis booster doses, not only to guard themselves against the debilitating infection, but also to decrease the chances of spreading the disease to unprotected babies and young children.
Recommendations for pertussis booster doses
To extend pertussis protection in older children, adolescents and adults, below are the current recommendations from the CDC and Advisory Committee on Immunisation Practices.
- Children aged four to six years are recommended to receive the fifth dose (or the booster dose) of the Tdap vaccine.
- Adolescents aged 11 to 18 years should get a single dose of Tdap. This dose is recommended for those who received DTaP shots as children but have not gotten a Td (tetanus diphtheria) booster. Adolescents who have received a dose of Td are also encouraged to get a dose of Tdap for protection against pertussis.
- Adults aged 19 to 64 years should receive a dose of Tdap to replace a Td shot for booster immunisation.
- Adults who have close contact with babies younger than 12 months should get a dose of Tdap to avoid contracting and passing the disease to the babies. These include new parents, grandparents, maids, and childcare providers. Healthcare workers who have direct contact with patients in clinics and hospitals should also get a dose of Tdap.
It is also advisable that travellers get their pertussis booster shots before going out of the country, as pertussis remains frequent in parts of the world where vaccination levels are low. A booster dose will help to reduce the risk of travellers' contracting the disease while abroad and bringing it home.
Datuk Dr Zulkifli Ismail is a consultant paediatrician & cardiologist. This article is courtesy of Positive Parenting Programme by Malaysian Paediatric Association and supported by an educational grant from Sanofi Pasteur. The opinions expressed in the article are the view of the author.