We're Not Using One of Our Best Weapons against Drug-Resistant Microbes
Antimicrobial resistance (AMR) has been hailed as one of the biggest threats to humanity. The number of deaths caused by drug-resistant bacteria is expected to rise from 700,000 to 10 million a year by 2050. But while the challenges of developing new classes of antibiotics and reducing the use and misuse of existing drugs have dominated the headlines, there is a more immediate and complementary solution: vaccines. Vaccination not only prevents the spread of these bugs and prevents resistance from occurring, but it also significantly curtails the use of drugs every year by preventing infections in the first place.
While this places immunization on the frontline in the fight against AMR, that is not by design; it is a coincidence. Even though it is now widely recognized as one of the most effective ways of reducing the spread of AMR, our use of vaccines is still aimed primarily at reducing deaths and illness caused by infectious disease. That means we are failing to fully exploit one of our most powerful weapons against drug resistance. But if we made AMR a core part of our global vaccine strategy—dictating how we prioritize and incentivize the use of existing vaccines and the development of new ones—then we could achieve so much more. Until we do, we’re not doing all we can to beat AMR.
There are three main paths we should follow. The first involves doing what we’re already doing, but more. Take the pneumococcal conjugate vaccine (PCV), for example, which prevents the most common forms of bacterial pneumonia. Within the first five years of its introduction in the U.S. in 2000, it was found to reduce the prevalence of multidrug-resistant strains by 57 percent, and the number of cases of multidrug-resistant invasive pneumococcal disease (IPD) in children under two by 84 percent. Today, research suggests that universal coverage of this vaccine could prevent 11.4 million days of antibiotic use per year worldwide in children under five.
However, with only 44 percent of the world’s children receiving a complete course of PCV, we are far from exploiting its full potential. So, we really need to do everything in our power to make sure more people get this important vaccine. Similarly, Haemophilus influenza type b (Hib) vaccine has been shown to reduce antibiotic use, and some vaccines that prevent viruses—such as seasonal flu shots and measles—can help reduce inappropriate use of antibiotics, when people are misdiagnosed as having bacterial infections and treated.
Secondly, we need to prioritize new vaccines that can help reduce the spread of AMR. To some extent this has already begun. In the past, vaccines were assessed only on their direct ability to reduce mortality and morbidity, and to prevent epidemics, and on their value for money in doing so. But now in the coming months we’ll see the first large-scale uses of a vaccine that also has a potentially huge role to play in reducing AMR.
This is a vaccine that protects against typhoid, which is one of the biggest drivers of drug resistance. Pakistan, for example, has been battling with an outbreak of extensively drug-resistant typhoid for the last two years (it resists five of the six recommended antibiotics—which has already been linked to cases among travelers returning to the U.S. The new typhoid conjugate vaccine (TCV) will help.
TCV is more effective than existing vaccines and offers longer protection, but it can also be given to younger children thereby covering a larger proportion of the population. In places like Karachi, where antibiotic resistance is increasing by 30 per cent annually and may reach a point where all cases will be resistant to multiple drugs as early as next year, having greater vaccination coverage to prevent the disease will go a long way. The vaccine has already been used locally to reduce the spread of the outbreak, and plans are in place to introduce this vaccination nationally later this year.
Less obvious examples include group A streptococcus, which kills around 300,000 people a year by causing rheumatic heart disease. Based on this alone, the funding a potential vaccine candidate might attract may or may not be enough to bring it to market. But if you factor the 615 million cases a year of strep throat that it causes, the case for such a vaccine becomes much stronger. Because if everyone with strep throat gets treated, with the recommended 10-day course of antibiotics, then that’s more than 6 billion days of antibiotic use we could prevent. Take other viral causes of a sore throat mistreated with antibiotics because of a fear of strep which if people were vaccinated for strep we could avoid, then the number gets even much higher.
A candidate vaccine for group A strep does in fact exist, but is still at an early stage of development. But the point is that, if solely assessed on its potential impact on mortality, it may never get much further as most of the cases of rheumatic fever are now in developing countries. And if we want to encourage research into vaccines for infections like salmonella, gonorrhoea and shigella, which the World Health Organization has identified as AMR priority pathogens, then we need stop just looking at how many people they directly kill.
So as the WHO Executive Board reviews the progress and discusses the challenges of AMR this week, we have to face up to the grim fact that it will take years or even decades to develop new antibiotics—and when they are developed, the cycle of resistance development will just begin anew. And yet there are vaccines already in existence and development that are not being deliberately targeted at AMR and so are not fully exploited. Given the right incentives they could expand our arsenal against AMR and make all the difference.