We've all grown up knowing that we need to get a tetanus booster at least once a decade in order to be protected from the potentially fatal disease.
That strategy has been incredibly safe and successful, with these days only around 31 cases of the disease being reported annually in the US. But a new study suggests that although there's nothing wrong with being overly cautious, we could still be protected from the disease by getting just one booster every 30 years - and save a whole lot of money in the process.
But before you go and play with some rusty nails to celebrate your extended protection, it's important to note that this is a preliminary study. For now, doctors in most countries still advise boosters every 10 years, and it's going to take a lot more validation and replication of these results before that changes.
That said, it's an interesting study that suggests we could continue to save lives, as well as saving the US government US$280 million each year, by switching the recommendation for tetanus and diphtheria boosters to every 30 years.
"We have always been told to get a tetanus shot every 10 years, but actually, there is very little data to prove or disprove that timeline," said lead researcher Mark K. Slifka from Oregon Health & Science University.
Tetanus and diphtheria are both transmitted by bacteria. Although they're now relatively rare in developed countries, thousands of people still die from the diseases in developing countries where there's less immunisation coverage, highlighting the importance of getting vaccinated against them.
Currently, the tetanus and diphtheria vaccinations are given together - either on their own or, more commonly, with the vaccination for pertussis (whooping cough).
This happens five times in the first four years of life to impart long-lasting protecting. And after that, people in countries such as the US and Australia are told to get boosters every 10 years.
But the new research looked into how long 546 adults were actually protected against diphtheria and tetanus, and found that they contained antibodies against the diseases for up to 30 years after receiving their last booster - way longer than previously assumed.
Using mathematical modelling, the team used these results to show that if the US switched from a 10-year to a 30-year vaccination schedule, the country would still maintain greater than 95 percent immunisation levels, and could also save around $280 million in healthcare costs in the process.
Not only that, but it'd be a hell of a lot easier to remember that you need boosters at 30, 60, and 90 years of age, rather than trying to count back every few years and remember when you last had an injection.
Before anything changes in the US, the Advisory Committee on Immunisation practices will need to review the data, says Slifka. But the World Health Organisation and the UK government have already moved away from recommending adult boosters every 10 years.
"Based on our results and the vaccination schedule already recommended by other countries and the World Health Organisation, it might not be long before we can say goodbye to the traditional 10-year booster program," says Slifka.
Of course, this whole system only works if kids get the recommended five doses during childhood - and just because tetanus and diphtheria are rare in developed countries now, doesn't make them any less deadly, or any less likely to come back if immunisation levels drop.
“We need to make sure our kids get all of their recommended vaccinations," says Slifka. "I can’t emphasise this enough. Only by getting the complete childhood series will these children grow into adults who will maintain strong vaccine-mediated protection against these important diseases."
But in the future, it might become a lot easier for us to keep up that protection throughout our lives.
The results have been published in Clinical Infectious Diseases.