Excessive and often irrational use of antibiotics has led to increased resistance of bacteria (and humans) to a very high number of drugs, which has significantly increased concerns about the implementation of possible therapies. On the other hand, vaccination is still the best way to prevent deadly diseases. Why do vaccines, unlike antibiotics, not cause the development of resistance, and thus continue to work successfully?
Bacteria and mechanisms of resistance
Although the number of approved antibiotics is constantly growing, patients’ resistance to drugs is growing in parallel. Bacteria have over time developed various resistance mechanisms which allow them to survive despite the drugs being used. It took only six years to develop resistance to penicillins, the first and most well-known antibiotics. To date, the resistance of bacteria to every antibiotic has been confirmed, making the success of infection therapy a new public health concern.
Enzymes such as beta lactamase or dehydropeptidase are just some of the “helpers” that bacteria can use to prevent the effects of drugs. Namely, beta lactamases attack the beta lactam ring of antibiotics, binding to it by an ester bond. Then comes the hydrolysis of the newly formed bond and the formation of an inactive, hydrolyzed drug that will not exert its effect. Additionally, during the multiplication of bacteria and viruses, mutations (changes in the genome) can occur, which may sometimes inhibit the binding of the drug to the microorganism and “help” the pathogens in action.
Number of targets
The use of a vaccine that contains a bacterial or viral antigen stimulates the body’s initial pathogen response and stimulates the production of immunoglobulins – antibodies that bind to the antigen. The immune system does not produce just one or a few antibodies, but an entire army of immunoglobulins that bind to different regions (epitopes) on an antigen. By binding to antigens, antibodies can prevent the pathogen from entering the cell or destroy it.
Antibiotics and antiviral drugs generally have a single target. For example, binding to proteins such as enzymes leads to their inhibition, making it impossible for pathogens to multiply or survive. Mutation of the drug binding site leads to the development of resistance to the drug, while mutation of the antigen introduced by the vaccine is possible, but much less common.
Number of pathogens
Antibiotic or antiviral therapy is initiated due to the presence of a high number of pathogens that have triggered the onset of infection or inflammation. Thus, the presence of only one or a few bacteria will not necessarily cause the symptoms to cause the patient to seek help. On the other hand, vaccines are used to prevent disease. Once a vaccinated person encounters a pathogen, antibodies previously formed during vaccination will work even at a low number of pathogens. Among other things, this is extremely important given that the likelihood of resistance increases with the increase in the number of pathogens in the body.
Of course, this does not mean that vaccine resistance has not occurred in the past or will not occur in the future. The influenza virus mutates very often, which is why there is a new (seasonal) vaccine every year that contains antigens of the currently present strain of the virus.
Should we worry, that long-awaited vaccines will lose their effectiveness and that the SARS-CoV-2 pandemic has no end? Fortunately, not all viruses have the same susceptibility to mutations, and in addition, the use of vaccines approved so far stimulates the production of antibodies that bind to different epitopes, thus reducing the possibility of resistance. Nevertheless, the emergence of new strains of the virus increases the likelihood that some of them will become “profitable”, i.e., that there will be a mutation that will require the development of new vaccines, and potentially cause a new pandemic. Therefore, in order to prevent the spread of the virus and save time for ourselves and scientists around the world, it is extremely important to respect epidemiological measures and to preserve ourselves and others as much as possible.
Translated by Filip Sakoman