Whooping cough infection trials safe at home, study shows

Deliberately infecting volunteers to test new whooping cough vaccines has been shown to be safe in research.

A team at University Hospital Southampton has developed a safe method of ‘controlled human infection’, where volunteers are infected with whooping cough bacteria without causing any illness. This can be used to study the infection in detail and to help develop and test new and improved vaccines.

The researchers have shown that the method was safe, even when volunteers went home while infected with the bacteria that causes the disease. The results have now been published in the Lancet Microbe.

Led by Southampton’s Professor Robert Read, the discovery marks a major step forward for whooping cough vaccine development.

It shows trial participants do not need to stay for weeks in hospital. This takes away a major barrier to developing a new, potentially life-saving vaccine.

The findings will speed up the testing of new vaccines for whooping cough and has international importance. In light of this evidence, the US government’s Food and Drug Administration has now stated that controlled infection studies can be used to assess the efficacy of new whooping cough vaccines.

The study was delivered through the NIHR Southampton Biomedical Research Centre (BRC).

Protecting babies

Whooping cough is estimated to cause 160,000 deaths worldwide each year. Half of these are in babies less than a year old.

Caused by the bacteria Bordetella pertussis, it is highly infectious and is spread through coughs and sneezes. The bacteria can infect the upper airway without causing disease symptoms, so adults can spread it without knowing they have it.

While infected adults can have mild cold-like symptoms or none at all, whooping cough can cause persistent coughing and breathing difficulties in babies under six months. This can be severe and even life-threatening.

A vaccine for whooping cough is currently offered to all babies in the UK. However, it does not offer lifelong protection, or prevent people from getting infected or spreading the disease.

We therefore need a better whooping cough vaccine to be developed.

Avoiding weeks in hospital

To investigate whether a whooping cough vaccine protects people against being infected or spreading it, you need to know people will be exposed to Bordetella pertussis.

Since this is unlikely to happen by chance in the UK, researchers are investigating whether trial participants can be deliberately infected under controlled conditions. This is known as a ‘human challenge trial’.

Previously, healthy volunteers deliberately infected with Bordetella pertussis were required to stay in isolation at hospital for around two weeks, before being given antibiotics to clear it.

Now, these new results show this may not be necessary. In this study, participants were treated as outpatients, meaning they were allowed to return home after being infected at the NIHR Southampton Clinical Research Facility.

Of the 51 adults who took part, the bacteria did grow in 23 of their noses. None developed symptoms of whooping cough and there were no serious side effects reported.

The study also tested 14 people who shared a bedroom with one of the participants. None of them became infected, showing the participants did not spread the bacteria.

Professor Read is senior author on the paper. He leads the NIHR Southampton BRC’s microbiology, immunology and infection theme.

“Our results show this new way of infecting healthy volunteers is safe and effective,” he said.

“Isolating participants in hospital for weeks at a time is expensive, and prevents many people from being able to take part.

“We hope this new discovery will remove this barrier, enabling the development of a new vaccine that will better protect babies.”