Despite being fully vaccinated, an estimated 20 percent of children in the United Kingdom with a persistent cough likely have whooping cough, a recent study suggests, adding to an ongoing debate about the cost effectiveness of vaccination boosters.

The study, published in the British Medical Journal, details how researchers determined that approximately 18 percent of 279 children with persistent chough symptoms wound up having whooping cough, despite the fact that they had been fully vaccinated. Another 2 percent of the group had been partially vaccinated (without finishing the vaccination regimen) and still tested positive for whooping cough.

Interestingly, according to the study, the University of Oxford doctors and researchers involved were able to determine that vaccinated children five to 15 years old were three times more likely to contract whooping cough if they had received a booster shot more than seven years ago, compared to children who had recently received the booster in their adolescence.

"The results of our study will help inform ongoing discussions about whether an adolescent booster vaccination should be introduced in the UK," lead author Kay Wang told Medical News Today. "However, more evidence is still needed on the socioeconomic burden of whooping cough in this age group."

The ongoing debate in the UK mirrors a more general vaccination debate around the world. Cost effectiveness - if the costs of vaccination can be outweighed by the public safety gain - is extremely important in determining if a vaccination will be made widely public.

Still, there is little doubt that the whooping cough vaccination is needed. In the United States alone, whooping cough affects about 50,000 unvaccinated children and preteens a year, according to the US Centers for Disease Control and Prevention. Worldwide, an estimated 300,000 unvaccinated children still die from the illness when left untreated.

However, it has remained a state-by-state decision as to whether an adolescent booster shot would be required in public schooling systems - as the effectiveness of this booster shot remains controversial.

The study was published in the British Medical Journal  on June 24.