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We have been reading reports in recent times on how measles has been spreading in some parts of the world because people are refusing to get their children vaccinated. But now we found other alarming reports that say this problem is going deeper than we expected. 

Children who survive measles are protected against future measles infections, but have such diminished immunity that they may be left vulnerable to other pathogens, according to a pair of research papers in Science (1) and Science immunology (2) published recently.

The studies, which examined blood from unvaccinated children, show that the virus decimates the body’s reserves of pathogen-specific immunological weapons. They provide “real evidence-based data to argue for the importance of vaccination.

The measles virus causes a short-lived illness characterized by fever, fatigue, and a distinctive rash. In some cases, however, the virus, which attacks immune cells, leads to serious complications and even death. Before the measles vaccine was available, almost every child experienced an infection with this highly contagious virus. Since the vaccine’s introduction in 1963, there has been a steadily diminishing number of measles cases worldwide and, as a result, tens of millions of lives have been saved.

Image result for measles rash distribution

Measles rash image

Source : Google images

Since 2018, this downward trend has reversed. Largely because of reduced numbers of vaccinations, there has been almost three times as many cases reported worldwide in 2019 as there were last year. The reversal is particularly concerning because the vaccine is thought to protect children from more than just measles. 

In the 1960s and ‘70s, every time the vaccine was introduced in a new region, childhood mortality would plummet beyond what could be explained by preventing measles alone.

One theory behind the unexpectedly large drops in mortality was that the vaccine prompted a general boost to the immune system. Population studies of measles epidemics, however, revealed that in the months and even years following outbreaks, the numbers of deaths caused by other infectious agents also increased. This suggested that measles made sufferers susceptible to other deadly infections, and therefore that, by preventing measles, the vaccine also prevented such weakening of the immune system. This epidemiological evidence was strong.

Now we have biological data from these studies which confirm what scientists feared all these days.

The researchers examined blood samples collected from 77 unvaccinated children—members of religious communities who choose to forgo vaccinations—before and after natural measles infections. The team also studied samples from a further five unvaccinated children who did not catch the virus as well as 59 age-matched, vaccinated controls.

The blood was analyzed using a tool called VirScan, which detects the presence of antibodies against thousands of epitopes representing more than 400 viral and bacterial human pathogens. The assay revealed that, after a measles infection, the diversity of a person’s antibodies dwindles. some of these effects were drastic. 

 Indeed, the children lost between 11 percent and 73 percent of their antibody repertoire, meaning their immunological memories of previously encountered pathogens would be impaired. No such loss was seen in the unvaccinated children who did not suffer measles infection or the vaccinated controls. The researchers also observed a similar loss in antibody diversity in unvaccinated macaque monkeys infected with the measles virus.

In the Science Immunology paper, immunogeneticists of the Wellcome Sanger Institute and colleagues examined B cell receptor sequences in the same blood samples. B cell receptors are essentially non-secreted versions of antibodies that reside in B cell membranes. The team found that, as with the antibodies, there was a dramatic loss of prior antigen-specific B cell receptor sequences as a result of measles infection.

From these two independent studies, scientists  show a very similar general picture about how important it is to vaccinate against measles not only to protect children from this deadly disease but also from the other ones too. 

References: 

1. M.J. Mina et al., “Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens,” Science, 366:599–606, 2019.

2. V. N. Petrova et al., “Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles,” Sci Immunol, 4:eaay6125, 2019. 

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