2. How might a person find more information about a vaccine? 3. Why should some people not get the MMR vaccine?

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1 Vaccines & Herd Immunity Text adapted from and [Retrieved Feb 2015] PART A: INDEPENDENT READING. On your own, read the following information on vaccines from the US Department of Health and Human Services. Then use that passage and the Vaccine Information Sheet on pg 2-3 to answer the Thinking Questions below. Understanding the difference between vaccines, vaccinations, and immunizations can be tricky. Below is an easy guide that explains how these terms are used: A vaccine is a product that produces immunity from a disease and can be administered through needle injections, by mouth, or by aerosol. A vaccination is the injection of a killed or weakened organism that produces immunity in the body against that organism. An immunization is the process by which a person or animal becomes protected from a disease. Vaccines cause immunization, and there are also some diseases that cause immunization after an individual recovers from the disease. Safety Vaccines are the best defense we have against serious, preventable, and sometimes deadly contagious diseases. Vaccines are some of the safest medical products available, but like any other medical product, there may be risks. Accurate information about the value of vaccines as well as their possible side-effects helps people to make informed decisions about vaccination. Federal law requires that Vaccine Information Statements explaining vaccine benefits and risks be provided when certain vaccinations are administered (before each dose). Vaccine Information Statements are available in Spanish and many different languages. In addition, more detailed information describing the benefits and risks of vaccines is available in the Prescribing Information from the Food and Drug Administration. Thinking Questions 1. How might a person become immunized? 2. How might a person find more information about a vaccine? 3. Why should some people not get the MMR vaccine? 4. What supports are available for someone who becomes sick or injured from a vaccine?

2 MMR Vaccine What You Need to Know VACCINE INFORMATION STATEMENT (Measles, Mumps and Rubella) Many Vaccine Information Statements are available in Spanish and other languages. See Hojas de información sobre vacunas están disponibles en español y en muchos otros idiomas. Visite 1 Why get vaccinated? Measles, mumps, and rubella are serious diseases. Before vaccines they were very common, especially among children. Measles Measles virus causes rash, cough, runny nose, eye irritation, and fever. It can lead to ear infection, pneumonia, seizures (jerking and staring), brain damage, and death. Mumps Mumps virus causes fever, headache, muscle pain, loss of appetite, and swollen glands. It can lead to deafness, meningitis (infection of the brain and spinal cord covering), painful swelling of the testicles or ovaries, and rarely sterility. Rubella (German Measles) Rubella virus causes rash, arthritis (mostly in women), and mild fever. If a woman gets rubella while she is pregnant, she could have a miscarriage or her baby could be born with serious birth defects. These diseases spread from person to person through the air. You can easily catch them by being around someone who is already infected. Measles, mumps, and rubella (MMR) vaccine can protect children (and adults) from all three of these diseases. Thanks to successful vaccination programs these diseases are much less common in the U.S. than they used to be. But if we stopped vaccinating they would return. 2 Who should get MMR vaccine and when? Children should get 2 doses of MMR vaccine: First Dose: months of age Second Dose: 4 6 years of age (may be given earlier, if at least 28 days after the 1st dose) Some infants younger than 12 months should get a dose of MMR if they are traveling out of the country. (This dose will not count toward their routine series.) Some adults should also get MMR vaccine: Generally, anyone 18 years of age or older who was born after 1956 should get at least one dose of MMR vaccine, unless they can show that they have either been vaccinated or had all three diseases. MMR vaccine may be given at the same time as other vaccines. Children between 1 and 12 years of age can get a combination vaccine called MMRV, which contains both MMR and varicella (chickenpox) vaccines. There is a separate Vaccine Information Statement for MMRV. 3 Some people should not get MMR vaccine or should wait. Anyone who has ever had a life-threatening allergic reaction to the antibiotic neomycin, or any other component of MMR vaccine, should not get the vaccine. Tell your doctor if you have any severe allergies. Anyone who had a life-threatening allergic reaction to a previous dose of MMR or MMRV vaccine should not get another dose. Some people who are sick at the time the shot is scheduled may be advised to wait until they recover before getting MMR vaccine. Pregnant women should not get MMR vaccine. Pregnant women who need the vaccine should wait until after giving birth. Women should avoid getting pregnant for 4 weeks after vaccination with MMR vaccine.

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4 PART B: INDEPENDENT READING. On your own, read the following information on vaccines from the US Department of Health and Human Services. Then answer the Thinking Questions below. Effectiveness Vaccines work really well. Of course, no medicine is perfect but most childhood vaccines produce immunity about % of the time. What about the argument made by some people that vaccines don t work that well... that diseases would be going away on their own because of better hygiene or sanitation, even if there were no vaccines? That simply isn t true. Certainly, better hygiene and sanitation can help prevent the spread of disease, but the germs that cause disease will still be around. As long as germs still exist, they are they will continue to make people sick. All vaccines must be licensed (approved) by the Food and Drug Administration (FDA) before being used in the United States. A vaccine must go through extensive testing to show that it works and that it is safe before the FDA will approve it. Among these tests are clinical trials, which compare groups of people who get a vaccine with groups of people who get a "control" (e.g, either a different vaccine or placebo). A vaccine is approved only if FDA determines that it is safe and effective for its intended use. If you look at the history of any vaccine-preventable disease, you will virtually always see that the number of cases of disease starts to drop when a vaccine is licensed. Here s a chart showing this pattern for measles: Measles vaccine was licensed in 1962, and as you can see, that s when the number of cases started to decline. (Measles didn t completely disappear after 1993; there have just been too few cases to show up on this graph.) If the drop in disease were due to hygiene and sanitation, you would expect all diseases to start going away at about the same time. But if you were to look at the graph for polio, for example, you would see the number of cases start to drop around 1955 the year the first polio vaccine was licensed. If you look at the graph for Hib (a vaccine for a serious form of the flu that causes brain swelling and deafness), the number drops around 1990, for pneumococcal disease around 2000 corresponding to the introduction of vaccines for those diseases. Prevention Infections are the most common cause of human disease. Disease-causing microbes (pathogens) attempting to get into the body must move past the body s external armor, usually the skin or cells lining the body s internal passageways, and your immune system if these microbes get inside. Your immune system works because is able to tell if an invader (virus, bacteria, parasite, or other another person's tissues) has entered it even if you aren't consciously aware that anything has happened. Your body recognizes this invader and uses a number of different tactics to destroy it. Vaccines help the body s immune system prepare for future attacks. Vaccines consist of killed or modified microbes, parts of microbes, or microbial DNA that trick the body into thinking an infection has occurred. A vaccinated person s immune system attacks the harmless vaccine and prepares for invasions against the kind of microbe the vaccine contained. In this way, the person becomes immunized against the microbe: if re-exposure to the infectious microbe occurs, the immune system will quickly recognize how to stop the infection.

5 Thinking Questions 1. What must happen before a vaccine becomes licensed in the United States? Why do you think we have this process? 2. A placebo is a medically ineffective treatment for a disease or medical condition. Its purpose is to make a patient believe he is getting treatment when he is not. In true clinical trials, a set of patients are given a real vaccine while others receive the placebo, or control. Why do you think the scientists who run the clinical trials pretend to treat some of their patients? 3. What evidence do scientists have that vaccines control or eradicate diseases over time? How do they know this is not due to just a natural dying of the disease, or better hygiene practices? PART C: INDEPENDENT READING. On your own, read the following information on herd immunity PBS NOVA. Then answer the Thinking Questions below. The term herd immunity refers to a means of protecting a whole community from disease by immunizing a critical percentage (the critical mass ) of the population. Vaccination protects more than just the vaccinated person. By breaking the chain of an infection s transmission, vaccination can also protect people who haven t been immunized. But to work, this protection requires that a certain percentage of people in a community be vaccinated. What factors determine where that critical-mass threshold lies? And once it s in place, how does herd immunity cocoon the most vulnerable among us? 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 infection from reaching them and limiting potential outbreaks. Every vaccinated person adds to the effectiveness of this community-level protection. What do the 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.

6 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 seven. 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. The general concept of an immunity threshold seems simple, but the factors involved in calculating a specific threshold are complex. These factors include how effective the vaccine for a given disease is, how long-lasting immunity is from both vaccination and infection, and which populations form critical links in transmission of the disease. The collective differences in these factors result in different thresholds for different diseases (see right), with a significant factor being R0. Why is herd immunity important? Human communities were once relatively small and isolated. Diseases certainly broke out, but their transmission ended wherever geography limited a populace s mobility. But today, our chains of connection traverse the globe reaching across oceans and over mountain ranges, pervading immense cities and remote villages linking us all into one vast, interactive human herd. Almost no one anymore lives in isolation from such connections. These chains of human interaction have resulted in more potent chains of disease transmission. The only thing that can break a chain of transmission is a disease-resistant link. The chicken pox vaccine offers an example of the effectiveness of disease-resistant links. After the chicken pox vaccine debuted in the United States in 1995, deaths rates from chicken pox dropped by as much as 97%. Significantly, even though the vaccine is not administered to infants, no infants died from chicken pox in the United States between 2004 and These tiniest, most vulnerable links in the chain of human connections avoided exposure thanks to herd immunity. Thinking Questions 1. Explain, in your own words, herd immunity. 2. What are immunity thresholds, and why are they important in public health? 3. Explain in your own words what R0 tells you about a disease. What does measles R0 of mean? 4. A health issue appearing in the news recently is the fact elementary schools are seeing a drop in child immunizations for example, some schools are reporting 75% immunization for measles, mumps, and rubella. What might this mean for that school or that community?

7 PUTTING IT ALL TOGETHER -- Use the disease transmission simulator at supplements/nih1/diseases/activities/flash- detection.htm to answer the questions below. In this activity, you will be using a computer Disease Transmission Simulator to observe the effect of four different disease characteristics on the spread of disease through a population: A. Initial percentage immune: Percentage of the population already immune. In this simulation, initial immunity can range from 0 percent (no one immune) to 100 percent (everyone is immune). B. Virulence: Likelihood of dying from the disease. In this simulation, virulence ranges from 0 (no victims die) to 0.75 (75 percent of the victims die). C. Duration of infection: Length of time the disease is active. In this simulation, infections can last from 1 to 20 days. D. Rate of transmission: Number of new people infected each day. In this simulation, rate of transmission ranges from 0.1 per day (1 person every 10 days) up to 10 new infections per day. Simulator Instructions 1. Set the desired values for the disease characteristics. 2. Click Autorun (automatically runs for 30 days) or Run Day- by- Day (allows you to step through 30 or fewer days). 3. Click Reset to start a new run using the same or different values for the disease characteristics. Note the dotted line on the graph, which indicates an epidemic has occurred. A. Initial Percentage Immune Test the impact of different levels of initial percentage immune. Keep other values constant at Virulence=0.15 Duration of infection=3 Rate of transmission=2 Initial Percentage Immune Maximum Percentage Sick The Day Maximum Occurred Epidemic Level? 0% 30% 60% Summary: When you start with a higher percentage of the population immune, is the community more or less likely to experience an epidemic? Explain. B. Virulence Test the impact of different levels of virulence. Keep other values constant at Initial percent immune=25 Duration of infection=3 Rate of transmission=2 Virulence Maximum Percentage Sick The Day Maximum Occurred Epidemic Level? Summary: As virulence, or deadliness of the disease, increased, was the community more or less likely to experience an epidemic? Explain. (Hint: consider the population, which started at 100,000 people)

8 C. Duration of Infection Test the impact of different durations of infection. Keep other values constant at Initial immunity=25 Virulence=0.15 Rate of transmission=2 Duration of Infection 1 Maximum Percentage Sick The Day Maximum Occurred Epidemic Level? 5 10 Summary: As duration of infection increased, did the likelihood of an epidemic increase or decrease? Explain. D. Rate of Transmission Test the impact of different rates of transmission. Keep other values constant at Initial immunity=25 Virulence=0.15 Duration of infection=3 Rate of Transmission 0.5 Maximum Percentage Sick The Day Maximum Occurred Epidemic Level? Summary: As the rate of transmission increases, the likelihood of an epidemic because Herd Immunization Using the Disease Transmission Simulator, find the minimum percentage of people required to be immunized to achieve herd immunity for each of the diseases below. [The minimum level occurs when the red line rises to meet the horizontal Epidemic Level line, but does not rise above it.] Disease Characteristics (approximations) Disease Transmission Virulence Mumps Meningococcal Meningitis Chicken Pox Airborne, droplets Direct contact, droplets Direct contact, droplet, airborne Duration of Infection Rate of Transmission low (0.01) 14 days high (2.5) med (0. 15) 10 days low (0.2) low (0.01) 7 days very high (10) Immunization Level for H. I. Smallpox Direct contact high (0.3) 14 days high (2.5) Polio Fecal- oral route low- med (0.12) 18 days average (1) Measles Airborne low (0.01) 8 days very high (10) Note: Smallpox is the only virus to have been eradicated worldwide through global vaccination efforts. The smallpox virus only exists in laboratories. Also, sources claim the United States stockpiles enough of the vaccine to vaccinate every American. Certain populations are at more risk for certain diseases such as the many forms of meningitis, which in the United States typically affect students and people in crowded environments. In crowded environments, the disease s rate of transmission will usually be higher.