Are vaccines the demise of superbugs?
If no action is taken now, more than ten million people will die worldwide every year from multi-resistant bacteria, according to a study conducted by KPMG consultancy at the request of the British government.
On the other hand, a document from the World Bank Group (made up of 189 countries) indicates that, by 2050, drug-resistant infections could reduce global GDP by between 1.1% (in a so-called low-impact scenario) and 3.8% (in the high-impact scenario). Poor countries would be most affected, both in terms of the number of victims and the economic cost.
This global emergency forces the search for new tools against superbugs that current drugs can no longer deal with. This is what Ennio De Gregorio, head of the Vaccine Research Centre of the pharmaceutical company GSK in Italy, said: "Vaccines are essential in the fight against antibiotic resistance because a single medical strategy is no longer sufficient. They prevent infections, which reduces the circulation of bacteria and therefore the use of antibiotics that fight them, but they also cause them to evolve and gain resistance".
Tuberculosis
The effectiveness of vaccines against the strengthening of bacteria is being investigated in a microorganism that has the highest mortality rate: Mycobacterium tuberculosis. A bacteria which is responsible for most cases of tuberculosis. According to the WHO, 1.5 million people died from this infection in 2018, and it is estimated that a quarter of the world's population carries the bacteria.
Ten per cent of carriers will develop pulmonary tuberculosis, especially in undeveloped countries where access to diagnostics and drugs is very limited. Multi-drug resistant strains of Mycobacterium tuberculosis are emerging and spreading worldwide. The only vaccine (available since 1921) is BCG, named after the modified bacterium that constitutes it: the Calmette-Guérin bacillus. But it does not provide proven and consistent protection to adults in states plagued by endemic tuberculosis.
Recently, GSK brought hope by announcing that a clinical trial done with its experimental vaccine M72/AS01E1 significantly reduced the incidence of the disease in adults with latent infection (carriers of the bacteria who have not yet developed the disease). This vaccine is not applicable to patients with HIV.
The New Delhi enzyme
There are other cases that demonstrate the great danger of resistance to antimicrobial drugs. One of the most worrying is that of the New Delhi enzyme or NDM-1, which makes the bacteria that possess it almost immune to antibiotics, including those of the carbapenem family, the main therapeutic weapon against resistant strains. This enzyme has caused alarm in Tuscany in the past year where more than a hundred people have been infected.
The mortality rate caused by NDM-1 microorganisms ranges from 30 to 40% within 30 days of infection. The enzyme was first identified in 2008 in a Swedish patient from New Delhi. Experts sounded the alarm when the enzyme was detected in one in ten strains of Escherichia coli, one of the most common bacteria in humans.
