Scientists have known for a long time that measles affects the immune system, but the latest data suggest that it is not a mild weakening of the immune system, but rather a complete reboot. How dangerous is this in the context of mass vaccination against Covid-19?
It happened on the island of Upolu in the Samoan archipelago, a tiny emerald dot in the middle of the blue Pacific, halfway between Hawaii and New Zealand. Late in the evening of November 15, 2019, as the port city was already falling asleep, government officials rushed to a meeting to discuss an emergency situation. A few hours later, they declared a state of emergency, which took effect immediately.
Three months earlier, a local resident who had arrived from New Zealand, where a measles epidemic was raging, developed a characteristic reddish-brown rash on his body. A diagnosis of “suspected measles” was made, but the disease did not progress and no further action was taken. On October 2, seven cases of measles were reported on the island, but schools, which are the ideal place for the virus to spread because children are particularly susceptible, continued to operate as usual. Only school celebrations were temporarily banned, but this measure was ignored in some places. After a month, 716 of the island’s 197,000 inhabitants had fallen ill.
By declaring a state of emergency, the authorities resorted to radical measures. Schools, shops, factories and the airport were closed. Office workers were quarantined. Citizens were urged to stay home. The streets emptied and Upland became a ghost island.
Samoan authorities have so far been able to prevent the widespread spread of Covid-19. If it had, scientists say the population would have been at high risk. In a grim reminder of the red crosses on the doors of plague-ridden houses during medieval epidemics, red flags appeared on bushes, poles, and trees near the homes of unvaccinated families. Doctors went from house to house, vaccinating those who had not yet done so.
We explain quickly, simply, and clearly what happened, why it matters, and what happens next. The number of episodes should remain the same. End of story. Podcast advertising. The state of emergency was lifted on December 28. By that time, 5667 people on the island had recovered, including 8% of all children under the age of 15. 81 people died, including three children from the same family. The epidemic has ended, but it has not yet reaped its last harvest.
The people of Upolu have developed immune amnesia – a phenomenon that has existed for millennia, but was only discovered by science in 2012. After recovering from measles, a person loses immune memory for every pathogen they have ever encountered – every cold, every strain of flu, bacteria and viruses, and most importantly, every vaccination. The loss is almost complete and long lasting. The body has to learn again what is harmful and what is not in its environment.
“You could say that the measles virus resets the immune system as if it had never encountered microbes before,” says Mansour Haerifar, a professor of immunology at Western University in Canada. How does it work? How long does it last? Could it contribute to epidemics of other diseases?
Measles is a viral respiratory disease that is spread through airborne droplets. It is thought to have been transmitted to humans from domesticated animals about 2,500 years ago, possibly due to the emergence of densely populated cities. For thousands of years, measles easily affected children around the world. Rarely did anyone manage to avoid it before the age of 15. In 1967, the last year before measles vaccination in the United Kingdom, 406,407 people contracted the disease.
Europeans brought measles, smallpox, and typhoid fever to the New World, where they had not existed before. It is believed that the indigenous population of both Americas decreased tenfold within 100 years due to these diseases. Doctors have long known that children who have had measles are more susceptible to, and more likely to die from, other infectious diseases. According to a 1995 study, the measles vaccine reduces the risk of subsequent death by 30-86%. But no one understood why the measles virus was so powerful.
In 2002, a group of Japanese scientists discovered that the receptor to which the measles virus binds, a kind of molecular door through which it enters the body, is not located in the lungs, as one might expect, but in the cells of the immune system. “This came as a big surprise and was in stark contrast to what was written in textbooks about the spread of the measles virus,” says Rick de Swart, professor of virology at Erasmus University Rotterdam in the Netherlands. Another 10 years later, an international team of researchers, including de Swart, decided to take a closer look at the problem. They tagged measles viruses with a green fluorescent protein, infected macaques with them, and tracked where the tagged viruses ended up.
“We observed that the virus attacks cells sequentially,” explains de Swart. “This phenomenon is called viremia (the spread of viruses through the blood). Once in the bloodstream, the virus infects white blood cells, which then carry it to lymphoid tissues, such as the lymph nodes, spleen, and thymus (an organ in the upper part of the chest that is part of the immune system).” According to the professor, measles is actually an immune disease.
Before mass vaccination against measles began in Great Britain, schools were a breeding ground for the disease. The 2013 measles outbreak in the Netherlands provided an opportunity to test this theory. It began among members of the orthodox Protestant community, who refused vaccination for religious reasons, and subsequently affected about 2,600 people. Several years later, researchers took blood tests from recovered patients and found that their T lymphocytes, special cells produced by the thymus gland that play a key role in the body’s immune response, had been affected by the measles virus. But the story does not end there. The team found that the receptors to which measles viruses bind are the same T lymphocytes. They persist in the human body for decades, and their job is to recognize pathogens they have encountered before. In this way, measles affects cells, the carriers of immune memory.
“Measles suppresses and activates the immune system at the same time,” says Professor de Swart. “It erases immune memory, but with one exception. Remarkably, the only type of virus that can subsequently recognize measles-affected T lymphocytes is measles itself!” This inexplicable phenomenon has been dubbed the “measles paradox” by scientists. Measles causes an extremely strong immune response. Immunity to it is lifelong in the vast majority of people. How this relates to the suppression of immunity to other diseases is unknown. One theory is that the immune system learns to recognize T lymphocytes infected with the measles virus and begins to hunt them throughout the body, eliminating carriers of immune memory for other diseases. As a result, measles replaces normal immune memory cells with those that can only respond to measles and nothing else. Immunity to measles develops while all other pathogens are forgotten. It is a rather strange strategy from the point of view of the measles virus.
Unfortunately, there is no upside to this phenomenon. There is no data that such a total reboot of the immune system can be beneficial for people suffering from its disorders. In any case, as de Swart notes, an artificial infection with the measles virus can only affect those who have never had measles and have not been vaccinated against it.
Samoa was under quarantine before Covid-19 because of measles. “There is a clear similarity between the measles virus and the HIV virus,” says de Swart. “Both affect the cells of the immune system and destroy them. The difference is that HIV does it gradually, but slowly, chronically. The immediate immune amnesia caused by measles is unique to humans. The plague and morbilliviruses have a similar effect on dogs and dolphins. It cannot be excluded that the mechanism in these cases is analogous.
After the immune amnesia opened up, the pieces of the puzzle began to fit together. With the loss of immune memory cells, the body must patiently relearn what it knew before. The 2015 study showed that this process can take up to three years. It takes about the same amount of time for a newborn to develop immunity to the most common pathogens. “Babies often catch colds and have gastrointestinal problems. They need time to adjust. The duration is about the same,” says de Swart. After recovering from measles, children are once again threatened by pathogens they have learned to fight. “Every time an infection enters the body, there is an increased risk of developing the disease. Maybe you have to get sick again with all the diseases to rebuild immunity,” de Swart notes. Not surprisingly, measles not only increases incidence but also mortality from other diseases. A 2015 study based on extensive statistical material suggests a link between periodic increases in infant mortality in the UK, US, and Denmark and outbreaks of measles. Vaccinating children against measles brings additional benefits in the form of reduced mortality from other diseases that are far greater than those from measles itself.
In summary, measles has a profound impact on the health of the population for years after each outbreak. Everything is connected. The primary cause of the measles epidemic in Samoa was an extremely rare, tragic event. Several years earlier, two nurses mistakenly mixed batches of vials and improperly mixed measles, mumps, and rubella vaccines, resulting in the deaths of two children. The nurses were jailed, but the painful incident led to widespread mistrust of vaccinations among islanders, and by the time of the 2019 outbreak, only 30 percent of the population had been vaccinated against measles.
The estimated population of the New World before the arrival of the Europeans was about 60 million people. After invading the island, the measles virus – one of the most contagious in the world, with an R coefficient of 12 to 18 (the number of people an infected person can infect on average) – found ideal conditions. Although the authorities were able to bring the situation under control, the outbreak had long-term consequences. As soon as one epidemic ended, another began – on November 27, 2020, the first case of Covid-19 was registered in Samoa. Thanks to its island location and strict quarantine measures, widespread distribution was prevented. Had this not been the case, experts estimate that the previous measles epidemic would have increased coronavirus morbidity by 8% and mortality by more than 2%. Most alarmingly, measles outbreaks following mass vaccination with Covid-19 can reduce herd immunity to zero.
After receiving a vaccination against coronaviruses and subsequently contracting measles, a person can say to himself: “Nonsense, what does this have to do with my protection against Covid-19? – says Michel Muñoz, professor of statistics at the University of Granada and a participant in one of the studies. – It is very likely that this is not the case. You have contracted measles and your protection is lost. You are no longer safe. Under pandemic conditions, it is highly undesirable to contract measles.
In this context, another important question arises: if you have already had measles, is it necessary to be vaccinated again against the corona virus? Professor de Sward says that people don’t usually do this, although he doesn’t think it’s a bad idea. “As far as I know, there are no specific recommendations anywhere, although it might be helpful,” he noted. “In any case, people who are not vaccinated against measles are a small minority, so there is probably no need for special programs. Everything should be done on an individual basis.”
The only simple but reliable advice is to get vaccinated against measles if you haven’t already. So you save precious immune memory built up over decades and get rid of the need for a hundred shots instead of one. In Russia, the incidence of measles has increased three and a half times in the past year. Experts believe that the main reason for this increase is a conscious refusal to be vaccinated. The BBC’s Russian Service explains whether measles should be considered a dangerous disease, why Russians fear complications from the vaccine, and how officials plan to punish those who refuse to be vaccinated.