Parents have been urged to ensure that their children are immunised against diphtheria infection which has a very high mortality rate, said Director-General of Health Datuk Dr Noor Hisham Abdullah.

Currently, he said diphtheria immunisation was included in the series of five vaccines namely Diphtheria, Pertussis, Tetanus, Polio and Haemophilus Influenza Type B.

It is given at the age of two, three and five months as a prime dose and 18 months as an added dosage, he said in a statement Monday.

Diphtheria infection is caused by the bacterium Corynebacterium diphtheria which is spread through respiratory droplets and infects the throat (tonsils and pharynx).

It produces toxin that causes inflammation in the throat and neck swelling that can lead to difficulty in breathing, paralysis and inflammation of the heart (myocarditis).

Dr Noor Hisham said a child from Kampung Bukit Malut in Langkawi, Kedah, who did not receive immunisation against diphtheria, reportedly died from the infection in November.

"The victim's next-of-kin were checked and only one of them had the symptoms of diphtheria," he said.

He said Kedah had also recorded one death due to diphtheria, which occurred in Kampung Bikan, Kulim in December 2014. The victim was also unimmunised with diphtheria vaccine.

Immunization coverage of more than 95 per cent in the community will create herd immunity and protect children from being infected.

"Children who have received complete immunisation will only get mild symptoms," he said.

Dr Noor Hisham said in Malaysia, suspected diphtheria patients would be given antitoxin immediately without having to wait for laboratory results because the spread of the toxins in the body could be life-threatening.

"Usually, diphtheria-infected patient needs seven to eight vials of anti-toxin with a cost of RM500 per vial, compared to the RM34 per one dosage vaccines which can protect against five diseases," he said.

He added that since diphtheria immunisation was included in the National Immunisation Programme in 1972, the diphtheria infection cases had declined drastically.

In the past five years, the highest number of diphtheria cases was in 2013, when four cases, including two deaths, were recorded with an incidence rate of 0.01 per 100,000 population, he said.