This media release was issued by the Australasian Society for Infectious Diseases.
The Australian and other governments should rethink strategies to prevent whooping cough in newborn infants, including booster vaccination of siblings in addition to parents, grandparents and other close contacts of the baby, says a whooping cough expert.
In his address to the Australasian Society for Infectious Diseases (ASID) meeting in Adelaide (26-29 March), paediatrician and vaccine expert Dr Tom Snelling, Telethon Kids Institute, Perth, Australia, will also propose that Australia considers reintroducing one dose of the older 'whole cell' vaccine which provides the most durable protection, and furthermore, a booster vaccine should be given to children at 18 months, as already happens in most developed countries.
Currently in Australia, the whooping cough vaccine is recommended (and government funded) in a 3-dose schedule for infants at 2, 4 and 6 months of age, with boosters given at 4 years and at 10-15 years of age.
Whooping cough, also known as pertussis, saw notifications increase 4-5-fold in the years 2008-2012, with the greatest increase among school and pre school-aged children. "Improved detection of cases is part of the explanation. We propose that the switch from whole cell to acellular vaccines may also be partly responsible," says Dr Snelling.
"Data from our group and others show that protection from acellular vaccines is relatively short-lived, and animal studies suggest that while effective for personal protection, acellular vaccines are less effective than whole cell vaccines for reducing transmission of infection to others."
While vaccination of all pregnant women is already recommended in several countries and funded in the UK, in Australia this is not the case. In Australia, there is a permissive recommendation for vaccination in pregnancy, but no clear recommendation and no central funding.
Dr Snelling believes Australia and other countries should go further than this in their attempts to stop whooping cough in newborns, the group in which mortality is highest.
"There is a considerable reservoir of infection among older children and adults," says Dr Snelling.
"Booster vaccinating everyone is probably not going to be cost effective. However, it is likely we can improve protection for newborns by targeted vaccination or 'cocooning' , in which the pregnant mother-to-be, the father, grandparents and siblings are vaccinated in order to prevent transmission to the newborn infant."
Recent research by Snelling, along with Dr Helen Quinn and colleagues at National Centre for Immunisation Research and Surveillance and NSW Health showed that if both parents had received a booster dose of pertussis vaccine their newborn was about half as likely to develop pertussis compared to infants in households where neither were immunised; however no benefit could be shown if vaccination of the mother was delayed until after delivery.
"This was the first study to show that newborn infants can be indirectly protected by vaccinating parents," says Snelling, who with Quinn and colleagues has submitted the research for publication in a medical journal.
He adds: "The UK and USA have moved ahead of Australia to clearly recommend routine immunisation in pregnancy. I think on the basis of our data Australia should follow suit before the next epidemic occurs. In the meantime we may have data from the UK or US that proves what we suspect - that immunising in pregnancy is, in fact, the optimal strategy."
Booster vaccination of siblings is a controversial proposal, as Dr Snelling is suggesting all siblings of the newborn should also be given a booster vaccination if they have not been vaccinated in the previous 2-3 years before the birth of their new baby brother or sister. This would include most 3 year olds and most primary school aged children.
Work from his group and others have shown that older siblings are an important and under-recognised source of infection for young infants, and that children become susceptible to infection 2 to 3 years after their last vaccine dose. However, without government funding, vaccinating all close contacts of the child to be born could prove costly for families, with booster doses currently costing around AUD$50 each.
In terms of the type of vaccine used, Australia and many other countries have switched to new acellular vaccines as they are less reactogenic (ie cause less short term side effects) than the older whole cell vaccines.
Snelling states that a major problem with pertussis is that its intrinsic infectivity is so high that most of the population needs to be immune to infection to prevent transmission.
"We were closer to this goal with some of the good quality whole cell vaccines than we are with acellular vaccines. It is likely that substituting even a single acellular dose with a whole cell dose would improve the effectiveness of the current strategy," he says.
"Doing this, along with vaccinating routinely in pregnancy, vaccinating other close contacts of the newborn, and giving a booster vaccine in the second year of life, could all be strategies Australia adopts until such time as a new vaccine is developed that is more efficacious than the current acellular vaccines."
Dr Snelling's proposals to give booster vaccines to siblings of newborns who have not been vaccinated in the past 2-3 years, and use older whole cell vaccines, are not currently recommended anywhere.
He concludes: "While pertussis has declined in Australia since the last epidemic in 2012, its periodic resurgence in other wealthy countries means it is likely that Australia will have ever larger epidemics without new strategies."