Tag Archives: Public Health

Infectious Diseases Society of America study: Fatal measles case highlights importance of herd immunity in protecting the vulnerable

4 Nov

The Centers for Disease Control and Prevention (CDC) lay out the case for vaccination:
Why Are Childhood Vaccines So Important?

It is always better to prevent a disease than to treat it after it occurs.
Diseases that used to be common in this country and around the world, including polio, measles, diphtheria, pertussis (whooping cough), rubella (German measles), mumps, tetanus, rotavirus and Haemophilus influenzae type b (Hib) can now be prevented by vaccination. Thanks to a vaccine, one of the most terrible diseases in history – smallpox – no longer exists outside the laboratory. Over the years vaccines have prevented countless cases of disease and saved millions of lives.
Immunity Protects us From Disease
Immunity is the body’s way of preventing disease. Children are born with an immune system composed of cells, glands, organs, and fluids located throughout the body. The immune system recognizes germs that enter the body as “foreign invaders” (called antigens) and produces proteins called antibodies to fight them.
The first time a child is infected with a specific antigen (say measles virus), the immune system produces antibodies designed to fight it. This takes time . . . usually the immune system can’t work fast enough to prevent the antigen from causing disease, so the child still gets sick. However, the immune system “remembers” that antigen. If it ever enters the body again, even after many years, the immune system can produce antibodies fast enough to keep it from causing disease a second time. This protection is called immunity.
It would be nice if there were a way to give children immunity to a disease without their having to get sick first.
In fact there is:
Vaccines contain the same antigens (or parts of antigens) that cause diseases. For example, measles vaccine contains measles virus. But the antigens in vaccines are either killed, or weakened to the point that they don’t cause disease. However, they are strong enough to make the immune system produce antibodies that lead to immunity. In other words, a vaccine is a safer substitute for a child’s first exposure to a disease. The child gets protection without having to get sick. Through vaccination, children can develop immunity without suffering from the actual diseases that vaccines prevent.
More Facts
• Newborn babies are immune to many diseases because they have antibodies they got from their mothers. However, this immunity goes away during the first year of life.
• If an unvaccinated child is exposed to a disease germ, the child’s body may not be strong enough to fight the disease. Before vaccines, many children died from diseases that vaccines now prevent, such as whooping cough, measles, and polio. Those same germs exist today, but because babies are protected by vaccines, we don’t see these diseases nearly as often.
• Immunizing individual children also helps to protect the health of our community, especially those people who cannot be immunized (children who are too young to be vaccinated, or those who can’t receive certain vaccines for medical reasons), and the small proportion of people who don’t respond to a particular vaccine.
• Vaccine-preventable diseases have a costly impact, resulting in doctor’s visits, hospitalizations, and premature deaths. Sick children can also cause parents to lose time from work. https://www.cdc.gov/vaccines/vac-gen/howvpd.htm

A key component of the effectiveness of the effectiveness of vaccines is herd protection.

PBS NOVA reported in What is Herd Immunity?

What is “herd immunity?”
Just as a herd of cattle or sheep uses sheer numbers to protect its members from predators, herd immunity protects a community from infectious diseases by virtue of the sheer numbers of people immune to such diseases. The more members of a human “herd” who are immune to a given disease, the better protected the whole populace will be from an outbreak of that disease.
There are two ways an individual can become immune to an infectious disease: by becoming infected with the pathogen that causes it or by being vaccinated against it. Because vaccines induce immunity without causing illness, they are a comparatively safe and effective way to fill a community with disease-resistant people. These vaccinated individuals have protected themselves from disease. But, in turn, they are also protecting members of the community who cannot be vaccinated, preventing the chain of disease from reaching them and limiting potential outbreaks. Every vaccinated person adds to the effectiveness of this community-level protection.
What do thresholds have to do with herd immunity?
The microbes that cause disease all have different infectious features. Some, like measles and influenza, pass from person to person more easily than others. Some tend to have more severe consequences in specific demographic groups. For example, the symptoms of pertussis, or whooping cough, are distressing at any age but can be fatal in infants, the age group with the highest death rate from pertussis. Each of these features—such as transmissibility and severity—affects a given disease’s threshold, or the minimum percentage of immune individuals a community needs to prevent an outbreak.
To set a threshold, epidemiologists—experts in infectious disease transmission—use a value called “basic reproduction number,” often referred to as “R0.” This number represents how many people in an unprotected population one infected person could pass the disease along to. For example, R0 for measles is between 12 and 18, while for polio, it is between five and seve. The higher this number is, the higher the immunity threshold must be to protect the community. Because measles is extremely contagious and can spread through the air, for example, the immunity threshold needed to protect a community is high, at 95%. Diseases like polio, which are a little less contagious, have a lower threshold—80% to 85% in the case of polio….. https://www.pbs.org/wgbh/nova/article/herd-immunity/

Infectious Diseases Society of America (IDSA) reported about the importance of herd protection in cases where a disease can prove fatal with out herd protection.

Science Daily reported in Fatal measles case highlights importance of herd immunity in protecting the vulnerable:

Last year, a 26-year-old man receiving treatment for leukemia went to a Swiss hospital’s emergency room with a fever, a sore throat, and a cough, and was admitted. His condition worsened, and 17 days later, he died from severe complications of measles. The man’s weakened immune system was unable to fight off the disease, even though he was vaccinated against measles as a child.
A new report in Open Forum Infectious Diseases describes the man’s case, highlighting the importance of maintaining high vaccination coverage in the community to help protect people with compromised immune systems from measles and other vaccine-preventable infections. “Measles is not harmless, it’s a serious disease,” said the report’s lead author, Philipp Jent, MD, of Bern University Hospital and the University of Bern in Switzerland. “There is a responsibility to vaccinate yourself to protect others, not only to protect yourself.”
Following the patient’s admission in February of 2017, he developed additional symptoms over the next several days, including a progressive rash, mouth sores, and conjunctivitis, that suggested measles, although he had been fully vaccinated against the disease with the recommended two doses of the measles, mumps, and rubella (MMR) vaccine in the 1990s. A throat swab test confirmed the measles infection. Treatment with ribavirin (an antiviral drug), immunoglobulins (a type of antibody), and vitamin A did not improve his condition. He subsequently developed severe pneumonia and died.
The case illustrates how serious measles can be, particularly for people with compromised immune systems due to cancer treatment or other causes. It also underscores the importance of herd immunity in protecting these vulnerable individuals, the report’s authors noted. When vaccination rates in a community are high enough, vaccine-preventable diseases like measles are less likely to spread, which helps protect those who cannot be vaccinated (such as newborns not old enough to be immunized) or, like the patient in this case, for whom vaccines are not as effective.
When the proportion of people in a community who are vaccinated drops below this threshold, however, as it has for measles immunizations in several European countries, outbreaks are more likely. More than 41,000 children and adults in Europe were infected with measles during the first half of 2018, according to the World Health Organization, exceeding the annual total of European cases reported in any previous year this decade. In the U.S., there had been 142 confirmed cases of measles in 2018 as of early October, according to the U.S. Centers for Disease Control and Prevention (CDC). Data released by CDC in October also showed a gradual but concerning climb in the numbers of U.S. children who reach their second birthday without having received any recommended vaccines…. https://www.sciencedaily.com/releases/2018/11/181101133918.htm

Citation:

Fatal measles case highlights importance of herd immunity in protecting the vulnerable
Date: November 1, 2018
Source: Infectious Diseases Society of America
Summary:
A new report describes a recent case highlighting the importance of maintaining high vaccination coverage in the community to help protect people with compromised immune systems from measles and other vaccine-preventable infections.

Journal Reference:
Philipp Jent, Mafalda Trippel, Manuel Frey, Alexander Pöllinger, Sabina Berezowska, Rupert Langer, Hansjakob Furrer, Charles Béguelin. Fatal Measles Virus Infection After Rituximab-Containing Chemotherapy in a Previously Vaccinated Patient. Open Forum Infectious Diseases, 2018; 5 (11) DOI: 10.1093/ofid/ofy244

Here is the press release from IDSA:

Fatal Measles Case Highlights Importance of Herd Immunity in Protecting the Vulnerable
Last year, a 26-year-old man receiving treatment for leukemia went to a Swiss hospital’s emergency room with a fever, a sore throat, and a cough, and was admitted. His condition worsened, and 17 days later, he died from severe complications of measles. The man’s weakened immune system was unable to fight off the disease, even though he was vaccinated against measles as a child.
A new report in Open Forum Infectious Diseases describes the man’s case, highlighting the importance of maintaining high vaccination coverage in the community to help protect people with compromised immune systems from measles and other vaccine-preventable infections. “Measles is not harmless, it’s a serious disease,” said the report’s lead author, Philipp Jent, MD, of Bern University Hospital and the University of Bern in Switzerland. “There is a responsibility to vaccinate yourself to protect others, not only to protect yourself.”
Following the patient’s admission in February of 2017, he developed additional symptoms over the next several days, including a progressive rash, mouth sores, and conjunctivitis, that suggested measles, although he had been fully vaccinated against the disease with the recommended two doses of the measles, mumps, and rubella (MMR) vaccine in the 1990s. A throat swab test confirmed the measles infection. Treatment with ribavirin (an antiviral drug), immunoglobulins (a type of antibody), and vitamin A did not improve his condition. He subsequently developed severe pneumonia and died.
The case illustrates how serious measles can be, particularly for people with compromised immune systems due to cancer treatment or other causes. It also underscores the importance of herd immunity in protecting these vulnerable individuals, the report’s authors noted. When vaccination rates in a community are high enough, vaccine-preventable diseases like measles are less likely to spread, which helps protect those who cannot be vaccinated (such as newborns not old enough to be immunized) or, like the patient in this case, for whom vaccines are not as effective.
When the proportion of people in a community who are vaccinated drops below this threshold, however, as it has for measles immunizations in several European countries, outbreaks are more likely. More than 41,000 children and adults in Europe were infected with measles during the first half of 2018, according to the World Health Organization, exceeding the annual total of European cases reported in any previous year this decade. In the U.S., there had been 142 confirmed cases of measles in 2018 as of early October, according to the U.S. Centers for Disease Control and Prevention (CDC). Data released by CDC in October also showed a gradual but concerning climb in the numbers of U.S. children who reach their second birthday without having received any recommended vaccines.
“Ongoing efforts to raise confidence in vaccines and increase population immunity should be intensified,” the authors wrote in the case report’s conclusion. Physicians caring for people with compromised immune systems, the authors noted, should also ensure that those in close contact with these patients, such as family members and friends, are fully vaccinated.
Fast Facts
• People with weakened immune systems are at risk for contracting vaccine-preventable diseases, such as measles, even if they have been vaccinated.
• In this case, a 26-year-old Swiss man undergoing treatment for leukemia contracted measles and died from severe complications of the infection, despite being fully vaccinated against measles as a child.
• Maintaining high enough levels of vaccination coverage in the broader community, also known as herd immunity, can limit the spread of measles and other diseases and help protect those who are especially vulnerable.
Editor’s Note: The report authors’ affiliations, acknowledgments, and disclosures of financial support and potential conflicts of interests, if any, are available in the full report.
Fatal Measles Virus Infection After Rituximab-Containing Chemotherapy in a Previously Vaccinated Patient
https://academic.oup.com/ofid/article-lookup/doi/10.1093/ofid/ofy244

There is an ongoing public debate about possible risks of vaccination for some individuals vs. the greater good of vaccination for the commons.

Kevin M. Malone and Alan R. Hinman wrote in Chapter 13 of Vaccination Mandates: The Public Health Imperative and Individual Rights:

BACKGROUND
Concept for Community Disease Prevention
Garrett Hardin’s classic essay The Tragedy of the Commons3 describes the challenges presented when societal interest conflicts with the individual’s interest. Hardin notes the incentives present when the cattle of a community are commingled in a common pasture. At capacity, each owner still has an incentive to add additional cattle to the common because even though the yield from each animal decreases with the addition of more cattle, this decrease is offset for the individual owner by the additional animal. With this incentive, individual owners continue to add cattle to the commons to reap their individual benefit, leading to the inevitable failure of the common from overgrazing. The community interest in maximizing food production, therefore, can be achieved only by placing controls on the interests of the individual owners in favor of those of the community. Analogously, a community free of an infectious disease because of a high vaccination rate can be viewed as a common. As in Hardin’s common, the very existence of this common leads to tension between the best interests of the individual and those of the community. Increased immunization rates result in significantly decreased risk for disease. Although no remaining unimmunized individual can be said to be free of risk from the infectious disease, the herd effect generated from high immunization rates significantly reduces the risk for disease for those individuals. Additional benefit is conferred on the unimmunized person because avoidance of the vaccine avoids the risk for any adverse reactions associated with the vaccine. As disease rates drop, the risks associated with the vaccine come even more to the fore, providing further incentive to avoid immunization. Thus, when an individual in this common chooses to go unimmunized, it only minimally increases the risk of illness for that individual, while conferring on that person the benefit of avoiding the risk of vaccine induced side effects. At the same time, however, this action weakens the herd effect protection for the entire community. As more and more individuals choose to do what is in their “best” individual interest, the common eventually fails as herd immunity disappears and disease outbreaks occur. To avoid this “tragedy of the commons,” legal requirements have been imposed by communities (in recent times, by states) to mandate particular vaccinations.
Vaccine Safety and Effectiveness
Vaccines are safe and effective. However, they are neither perfectly safe nor perfectly effective. Consequently, some persons who receive vaccines will be injured as a result, and some persons who receive vaccines will not be protected. Most adverse events associated with vaccines are minor and involve local soreness or redness at the injection site or perhaps fever for a day or so. Rarely, however, vaccine can cause more serious adverse events. Whether an adverse event that occurs after vaccination was caused by the vaccine or was merely temporally related and caused by some totally independent (and often unknown or unidentified) factor is often difficult to ascertain. This is particularly problematic during infancy, when a number of conditions may occur spontaneously…. https://www.cdc.gov/vaccines/imz-managers/guides-pubs/downloads/vacc_mandates_chptr13.pdf

The issue for those balancing individual decision-making and the needs of public health are how much coercion is necessary to compel individual vaccination with the goal of protecting public health.

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