The US could be about eight months away from losing its "measles-free" status.
Measles virus was eliminated from the US in 2000, meaning that the disease has been continuously transmitted throughout the country for no longer than 12 months. Since then, the disease has occasionally risen because travelers, mostly Americans, have become infected abroad and are returning home. Although these outbreaks pose a threat to public health, especially for children and pregnant women, the incidents remain at individual sites – Anaheim, California, Winter 2015 or Minnesota – 2017 – and then go out.
This trend began to change last October when New York City ̵
If the US loses its status as a "measles disposal", it will join Venezuela as the only other country in North and South America with this distinction. Measles was declared eliminated throughout America in 2016, but within a year Venezuela erupted into an eruption that continues to this day.
For most Americans, these outbreaks are a bittersweet wake-up call about the importance of the measles-mumps-rubella (MMR) vaccine. Thanks to the success of vaccination programs, most people are not familiar with measles themselves – which means they are not sure how to manage and protect themselves from these outbreaks.
The PBS NewsHour presented these questions and concerns to two experts: Stephen Morse, director of the Infectious Disease Epidemiology Program at Columbia University's Mailman School of Public Health; William Moss, Epidemiologist of Infectious Diseases and Pediatrician at Johns Hopkins & # 39; Bloomberg School of Public Health.
Who is the most susceptible during a measles outbreak?
Morse: Children are usually the main targets, in part because the youngest children have no immunity at all.
Moss: Because the vaccine was so effective in the United States and around the world, I think people have forgotten about measles and underestimated measles risk. [Globally,] More than 100,000 children or about 300 children die each year. Measles can also cause lifelong disability [such as deafness].
Morse: The virus can slowly incubate in the brain for years. Then, as a rule, when the patient is much older [up to 10 years after a person has measles] the infection reactivates and you get this very severe progressive inflammation in the brain called Subacute Sclerosing Panencephalitis (SSPE)
[SSPE has long been considered rare, but a 2017 study from the California Department of Health estimated 1 in 600 infants developed the condition after they caught measles.]
What is If you are a healthy but unvaccinated adult – should you worry that you can catch the measles?
Morse: There are indeed serious complications that occur in unvaccinated adults who have measles, namely pneumonia.
Pregnant women are certainly at risk too. These problems may not be as well known as the Zika virus, but there are pregnancy complications of measles [such as stillbirths, miscarriages and low-birth weight]. There were many who walked around in earlier times.
[Pregnant women infected with measles are also more likely to be hospitalized, develop pneumonia, and die than nonpregnant women, according to the Centers of Disease Control and Prevention.]
That is, pregnant women should avoid the MMR vaccine for the same reason that a measles infection is so dangerous for them: their immune system is at risk. Once their child is born, they can safely vaccinate and breastfeed, for example. Should someone else avoid the vaccine?
Morse: People with immunosuppression or immunodeficiency who are considered rare exceptions.
We do not normally give the MMR vaccine right at birth? How is it?
Morse: In general, MMR vaccination prior to the age of [one] was not recommended because the feeling that children are younger does not respond and protection from measles develops – their immune system is not sufficiently mature.
In the event of outbreaks, doctors may postpone the envelope a little because of the increased likelihood of exposure. You may administer the vaccine after six months if there is some exposure risk, but this dose will not be considered for the child's vaccination schedule. In other words, the child has to take the other two doses if it is intended.
For children under 6 months, it is generally recommended to keep them away from people who may have measles, or from places where possible you could catch it.
The practice of giving Two doses of the MMR vaccine were launched in Sweden in 1982, but why?
Morse: They had noticed for years that children would go to school, and even though they had a vaccine, they could still catch measles if someone else came to school with measles it turns out that one Dose just does not provide adequate protection.
That's right, and finally, in 1989, the US Centers for Disease Control and Prevention passed the two-dose strategy, as the nation experienced a strong resurgence of measles that lasted until 1991. But how old do children need to be vaccines for their MMR now?
Moss: Later, the World Health Organization recommended that all children in the world receive two doses of measles vaccine. And the reason for the second dose is really because not all children who receive a single dose are protected.
In many parts of the world, the first dose is given at the age of nine months, and we generally see that about 85% of children are protected after this first dose. The second dose is for the most part immunization of 15% who did not respond to the first dose.
Now in the United States, we are giving the first dose at a higher age – usually between the ages of 12 and 20, 15 months old. There, a higher proportion of children will respond to the first measles vaccine in the order of 90 to 95%. The second dose is thus to receive this small proportion, perhaps 5 to 10% of the children who do not respond to the first dose.
Both inside and outside the US, this second dose is very important for elimination because measles are a very transmissible agent. We often say that it is the most contagious "directly transmitted pathogen," meaning that it spreads from person to person.
True, if a person gets measles, they will transfer to 18 other people if those people are not vaccinated. Therefore, the herd immunity or immunity of the community against measles can be maintained only if 90 to 95% of the population is immune.
Moss: To actually stop transmission and eliminate measles, we need a high degree of immunity in our communities. This is achieved with the two doses of measles vaccine.
But what if you are older and had measles as a child? Do you still need to get a shot?
Moss: This is somewhat arbitrary, but we generally say that people born before 1957 are immune, since almost everyone has previously had measles. The vaccine was introduced in 1963 in the United States.
Morse: And we believe that if you actually had it and recovered, you have a lifelong immunity, which is good.
Moss: So, there is no good evidence that a person has ever developed protective immunity to measles, either because they had the infection before or through the vaccine, and that protection diminishes over time.
But America has recently experienced riots, another mumps disease, caused by the attenuation of the vaccine.
Moss: That's a great question, and you're exactly right. What we have learned in the last few years due to major mumps outbreaks, especially at universities, is that immunity against mumps viruses is abating. For mumps outbreaks, it is recommended that people who have previously received a mumps vaccine receive an additional dose if they are exposed to a high exposure risk.
There is no indication that immunity to rubella is abating.
And if the immunity diminishes, a A real phenomenon in the measles vaccine, we would spread these outbreaks in the general population, especially the elderly, and we just do not see that.
Right. To summarize, when an adult catches the measles, it most likely means that as a child he never had the disease or received just one dose of the vaccine in his life. That is, if you were born between the late fifties and 1989, you might want to get another MMR shot?
Morse: Yes. What we tell people is when you're not sure what your vaccine status is, especially if you're traveling and taking another MMR.
What do you do if you can not remember if you have been vaccinated or lost your documentation?
Moss: There is a blood test to check for measles immunity. It can measure whether your body is producing antibodies to the measles virus. These antibodies have a pretty good correlation with the protection. It's what we call a serological test.
It is used, for example, for testing nurses. We want to ensure that hospital staff – nurses, doctors and other employees – are protected against measles, not only to protect the person, but also to prevent the spread of measles within a hospital.
At the moment it is not often used in outbreaks or in the general population. However, it is increasingly being used to identify susceptible groups of individuals outside the United States.
If you receive a second MMR after childhood or adulthood, how long will it take to take effect?
Moss: When we talk about the effectiveness of vaccines, we talk about their effectiveness in preventing disease.
… right, one dose yields 95% to 98% effectiveness, while two cans provide 99% protection …
Moss: It usually takes two to four weeks for a person to develop protective antibody levels ,
That's right, but does that mean some people can still get measles after two doses?
Morse: Given the nature of both statistics and the variation in human immune responses, this is possible.
Three percent of measles cases in Rockland County [New York] seem to have had two vaccines and therefore should not have caught the measles. They should be fully protected.
These cases suggest that the measles virus has evolved over time, like the seasonal flu virus, but in slow motion, rendering vaccines are less effective than they used to be?
Moss: The short answer is that there is no evidence that the measles virus has evolved over time. The measles vaccines used in the United States and around the world are derived from measles virus isolates dating from the mid-1950s.
Now people are looking for an evolution of the virus that we see in some other viruses – like the influenza virus, which is changing dramatically and we need to develop a new vaccine every year.
We do not have to do this with measles, and to date there is no evidence that the virus has evolved from its vaccine-derived protection.
Much of New York City's outbreak centered around Orthodox Jewish communities. From where?
Morse: Virtually every religion, including Islam, almost all Protestant sects, Catholicism and even ultra-Orthodox Judaism allowed vaccination without religious or theological objections. That is a good thing. It saves lives.
The outbreak this year is very much related to a subgroup of this ultra-Orthodox Jewish community.
This reflects the insularity of a particular group that does not trust the government – for the very same reasons you get in another group for vaccine hesitation or vaccine rejection.
They do not believe that the risk [of contracting measles] is so great. They are ready to take the opportunity. But it is a great opportunity, as we can see.