Charlotte A. Moser, assistant director, and Paul A. Offit, director, Vaccine Education Center at The Children’s Hospital of Philadelphia
Some believe that the lack of vaccine boosters given to adults provides evidence that herd immunity is a myth. So let’s look at this notion more closely.
Herd immunity is the concept that when most people in a community are protected against a disease, everyone in the community is better protected. A highly vaccinated community means that fewer people are available to spread viruses and bacteria, which results in lower levels of disease. Herd immunity does not apply for diseases in which person-to-person spread is not a means of transmission, such as tetanus.
While the general concept of herd immunity is the same for all transmissible diseases, the specifics of herd immunity vary depending upon the disease and vaccine used to prevent it:
When we put vaccine and disease factors together, each disease then has its own potential for the community to benefit from herd immunity. If you use the example of a ticket system, each vaccine-preventable disease, except tetanus, would be stopped in a community with only a certain limited number of “free-ride” tickets. Because some people in a community will be unable to get vaccinated for reasons such as age or health status, they will use these tickets. Likewise, people who choose not to immunize and those whose immunity is not protective will also be ticket holders. The more free-ride tickets in the community, the more likely the disease will enter the community. The diseases that can afford the fewest number of free-ride tickets before outbreaks occur are measles and pertussis. Because more and more people are asking for free-ride tickets, herd immunity has eroded and measles and pertussis outbreaks are occurring. Some authors refer to this problem as “the tragedy of the commons.”
Adults do not require as many immunizations as children because they are often immune to the diseases of childhood. For some, it is because they are old enough to have been exposed to the disease. For others, immunity is the result of vaccinations received earlier in life. However, because children often receive booster doses, people sometimes wonder why adults do not as well. The lack of need for booster doses in adult can be for one of several reasons.
Factors affecting the need for booster doses can be divided into those related to the disease and those related to the vaccine.
In summary, various factors make the potential for herd immunity different for each pathogen. In addition, whether or not booster doses are necessary depends upon both disease- and vaccine-specific characteristics. Therefore, the fact that booster doses are not typically necessary in adults cannot be used to prove or disprove the concept of herd immunity. A good rule of thumb when evaluating statements for accuracy is that broad, general statements often overlook nuances important in understanding a particular issue. So, while it might seem to make sense at face value that the lack of adult booster doses means herd immunity is a myth, taking time to explore the different aspects of the statement is important in sorting out whether the statement may be true.
Enterovirus D68 (EV-D68) has not garnered the media attention that Ebola virus has; however, it is more likely that you’ve encountered a patient with symptoms consistent with EV-D68. Unfortunately, fever, cough, runny nose, sneezing and body aches does not make for an open and shut diagnosis. In addition, it is likely that patients and families are on high alert and have many questions, especially with the cases of neurologic illness recently reported by the Centers for Disease Control and Prevention (CDC). For these reasons, we thought a background on enteroviruses might be of interest.
Enteroviruses are part of the Picornaviridae family. Viruses in this family are small-sized, single stranded RNA (ssRNA) viruses. The Picornaviridae family consists of 12 genuses, and within the enterovirus genus, 10 different species have been classified. Poliovirus, coxsackievirus and rhinoviruses are in the same genus as EV-D68.
|Virus||Species within the Genus|
|Enterovirus D68||Human enterovirus D|
|Polioviruses||Human enterovirus C|
|Coxsackieviruses||Human enterovirus A and B|
|Rhinoviruses||Human rhinovirus A, B and C|
Enteroviruses are fairly hardy. So they aren’t easily inactivated by common disinfectants, such as 70 percent ethanol, isopropanol, dilute Lysol® or quaternary ammonium compounds. Additionally, ether, chloroform and many detergents are also ineffective. As a general rule, enteroviruses are most effectively inactivated by formaldehyde, glutaraldehyde, strong acids, hypochlorite and free residual chlorine. However, a variety of factors play a role in the effectiveness of inactivation, such as concentration, pH, extraneous organic materials and contact time. Because enteroviruses tend to be sensitive to higher temperatures, pasteurization is effective for inactivating the virus in biological preparations. Ultraviolet light can inactivate the virus on surfaces and, generally speaking, viral titers decrease significantly when the virus dries on surfaces.
The two primary routes of infection for enteroviruses are respiratory and gastrointestinal (fecal-oral). In the case of EV-D68, the infection is primarily at respiratory sites. Therefore, transmission during the current outbreak is mostly expected to be through respiratory means – coughing, sneezing or self-inoculation through touching a contaminated surface or item and then touching one’s face.
Because of the relative hardiness of these viruses, the best way to avoid infection is to prevent inoculation by avoiding people who are sick, washing hands frequently, not touching one’s face with unwashed hands, and regularly cleaning objects that are touched often particularly by many people, such as doorknobs and toys. Patients with asthma should be also encouraged to maintain daily therapies.
More than one type of enterovirus is circulating and, of course, other respiratory viruses are also circulating. Typically, enteroviruses circulate between late summer and fall, so it is likely that they will soon be decreasing. However, an almost simultaneous uptick in influenza may make the appearance of infections characterized by respiratory symptoms seem steady.
Younger children, and those with respiratory conditions such as asthma, are more likely to suffer severe symptoms. However, those with asthma may also be more likely to suffer complications from infections with influenza or pneumococcus. Therefore, if a patient presents with severe respiratory illness and an unclear cause, EV-D68 testing may be considered.
Unfortunately, antiviral drugs that have been effective in treating other enteroviruses have not been effective against EV-D68 when tested at clinically relevant concentrations. Therefore, guidance should be to treat symptoms, and if the person has trouble breathing, he or she should seek emergency treatment.
Recent cases of neurologic illness with limb weakness are being investigated; however, it is still unclear whether these cases are causally associated with the ongoing EV-D68 outbreak. Enteroviruses are a known cause of neurologic illness in children; however, EV-D68 has previously been detected in cerebrospinal fluid (CSF) in a limited number of cases. However, among a cluster of nine patients in Colorado in August, CSF did not contain EV-D68, but 4 of 8 respiratory samples were positive for the virus. Because enteroviruses are common enough that sometimes they can be detected in healthy people, this finding alone does not establish causality between the neurologic illness and EV-D68 infection. The CDC continues to investigate these cases and has requested that clinicians report any patients with the following criteria to their state or local health department immediately:
Charlotte A. Moser, Assistant Director, and Paul A. Offit, Director, Vaccine Education Center at The Children’s Hospital of Philadelphia
Immunogenicity – a measure of the immune response generated after a person is vaccinated.
Efficacy – a measure of the decrease in likelihood of getting infected with or developing a disease after being vaccinated.
Immunogenicity and efficacy may be used interchangeably in conversations about vaccination; however, they are not exactly the same thing. This is especially true when discussing or interpreting data from vaccine trials.
Typically, the first clue as to whether a vaccine works is provided by measuring the immune response initially in experimental animals. Immunogenicity can be defined by any of the aspects of the immune response that are measurable. Most often for vaccines on the market, the measures are of antibodies in the blood, but in the research lab, measures can include newly formed or memory B cells, antibody secreting cells, or killer T cells to name a few. For some diseases, scientists know from previous work with the disease that if a person has a high enough level of one of these immune system components, he or she will be protected; this is called a correlate of protection.
If a correlate of protection is known and the potential vaccine does not induce a potent enough immune response, scientists need to reconsider the vaccine composition, dosage, and number and timing of doses. These studies can take years and are most often done in animals.
Unfortunately, for many diseases a clearly defined correlate of protection is not known. This is particularly true with infections that occur at mucosal surfaces (nose, throat, lungs, intestines and anogenital areas). In these cases, the most useful information comes from comparing the levels of the immune response following vaccination to those in individuals with disease.
While immunogenicity is helpful in assessing whether a vaccine is likely to work, it does not completely answer the question about whether the vaccine actually does work. That is, will a person who got vaccinated be protected if he or she is exposed to the disease? Efficacy data provides this information. As with immunogenicity, when researchers measure efficacy, they can measure a few different things. Most often they look at mild, moderate and severe disease which identifies everyone who gets ill, but by classifying severity of disease, the findings provides additional information about how the vaccine works. In cases of mild or moderate disease, the vaccine worked by altering the course of disease, and likely prevented some deaths, so it could still be considered valuable.
So, now you might be wondering why we still hear about immunogenicity data if efficacy data better defines how well a vaccine works. The answer is for a few reasons:
Immunogenicity and efficacy data provide information on how well a vaccine works, but they are not the same. So, if you are reviewing or explaining data, it is important to determine how the study was designed and what it measured in order to appropriately interpret the data.
Every month, Dr. Offit reviews a recent journal article; however, many other articles are published during the same period of time. This month in particular, a few articles and reports caught our attention and even though Dr. Offit is not reviewing them, we wanted to make you aware of them:
Three recent items may be of interest if you still have parents coming in with questions about autism and vaccines:
In the first five months of 2014, the United States has experienced more cases of measles than in the first five months of any other year since the disease was declared eliminated in 1994. Indeed, the U.S. Centers for Disease Control and Prevention (CDC) recently announced in the MMWR that to date, during 2014, 288 cases of measles have been diagnosed in 18 states and New York City. Of the cases, almost 80 percent were from 15 separate outbreaks with the largest occurring in Ohio among unvaccinated Amish communities. As of June 16, 2014, more than 400 cases of measles have been reported.
Increasingly, someone could come into your office ill with measles. For many healthcare providers, this has never happened before. In fact, in the CDC’s recent MMWR announcement, the authors indicated misdiagnoses of measles as Kawasaki disease, dengue and scarlet fever as well as other illnesses.
Measles diagnosis can be confused with other illnesses because of its common presentation as a rash accompanied by fever. When a patient has these symptoms, the following should also be considered to help distinguish measles from other possible illnesses:
Children presenting with measles typically appear to be miserable.
Measles is one of the most contagious diseases spreading most commonly, but not only, via large droplets. The virus is so contagious that if a susceptible person occupies an elevator or other enclosed space up to four hours after a person infected with measles, he or she is likely to be infected. The period of highest contagion is four days before to four days after onset of rash. Because of this ease of spread, it is imperative to isolate infected patients from susceptible patients, such as those who are too young to be immunized. Methods for decreasing chance of transmission in the waiting room include the following:
Current isolation precautions were published in 2007 and can be accessed online. Isolation procedures for infections transmitted via airborne routes in ambulatory settings can be found on pages 58-9 of the document.
Get a serum sample and throat or nasopharyngeal swab from the patient. A urine sample may also contain viral proteins. The most common tests are an IgM test and a real-time polymerase chain reaction (RT-PCR) test; either of these can typically be used for laboratory identification of measles. The CDC has a comprehensive section on its website related to measles lab tests.
Suspected cases of measles should be reported to local public health officials within 24 hours.
The MMR vaccine should be given at 12 to 15 months of age with a second dose between 4 and 6 years of age as recommended on the approved immunization schedule. The current measles outbreaks provide a compelling argument for not choosing to delay the MMR vaccine. Two studies provide additional reasons for children to be immunized as soon as they are of age:
Medscape recently posted a special report on measles with a wealth of information, including a two-and-a-half minute video by Dr. Offit discussing the recent cases of measles in the U.S.
Recently, we have had a spate of questions related to vaccines and allergies, so we thought it might be helpful to provide some additional information.
Peanut allergies – Children with peanut allergies do not need to forego any immunizations that might elicit a reaction.
Corn allergies – Similarly to peanut allergies, children with corn allergies are able to get all vaccines.
In the case of both peanut and corn allergies, the issue would be the oils contained in these products; however, neither of these oils are contained in vaccines. Some oil-in-water emulsions have been studied for use as adjuvants; however, a limited number have been licensed for use in Europe and none is approved for use in the United States. The European products contain squalene which is isolated from shark liver oil and is also produced in the human liver.
Egg allergies – Although people with egg allergies were previously cautioned against getting the influenza vaccine, current influenza vaccine products contain sufficiently fewer quantities of egg proteins than in the past. Therefore, only those with the most severe egg allergies (life-threatening) are cautioned about receipt. The 2013-2014 influenza season was the first in which a completely egg-free product, FluBlok®, was available.
Egg allergies are still a contraindication for receipt of the yellow fever vaccine. Someone with an egg allergy who is in need of the vaccine should consult with an allergist.
Gelatin allergies – Gelatin is used in some vaccines as a stabilizer. The type of gelatin in vaccines is derived from pigs, whereas the type of gelatin in most foods comes from cows. However, people with severe gelatin allergies have had reactions to vaccines. In fact, it is the vaccine ingredient responsible for the largest percentage of identifiable reactions. One anaphylactic reaction caused by gelatin occurs in about every 2 million doses of vaccine.
Vaccines containing gelatin and the quantity per dose are offered on the gelatin-specific page on our website.
Other food allergies – Yeast proteins are contained in vaccines including Pediarix® (< 5 percent), Twinrix® (< 5 percent), Energix® B (< 5 percent), Recombivax® (< 1 percent) and Gardasil® (< 7 mg). Vaccines that contain lactose include Hiberix® (12.6 mg per dose), Menomune® (2.5 to 5 mg) and Vivotif® (180 to 200 mg).
Latex allergies – Some vaccines are supplied in latex-containing packaging. Only those individuals with life-threatening (anaphylactic) allergies need to take precautions. In these cases, if it is determined that the risk of disease is greater than the risk associated with vaccination, the healthcare provider administering the vaccine should be prepared to respond to a reaction.
The CDC compiled a list of vaccines that contain latex and the part of the package that is affected. It is available in Appendix B of “Epidemiology and Prevention of Vaccine-Preventable Diseases (Pink Book) and has been updated online.
Antibiotics – During the manufacturing process, antibiotics are sometimes used to prevent contamination of vaccines. In some cases residual antibiotics remain; however, the antibiotics used in vaccines (neomycin, polymyxin B and gentamicin) tend to be different than those to which people experience allergic reactions (penicillins, cephalosporins and sulfa drugs). Additionally, most vaccines contain minimal to no antibiotics.
The vaccine ingredients – antibiotics page on the VEC website includes a summary table of the quantities of antibiotics in vaccines.
Ordering correct needles, stocking sufficient quantities of vaccine, checking refrigerator temperatures, scheduling appointments, answering questions. . . In the midst of all this work devoted to protecting patients from vaccine-preventable diseases, it is easy to forget its importance. That’s why every year for the past 20 years, the U.S. Centers for Disease Control and Prevention (CDC) has worked with communities to celebrate National Infant Immunization Week (NIIW), a week to remember, and celebrate, the lives saved by vaccination — approximately, 103 million lives since 1924 according to the recent paper by van Panhuis and colleagues. And, if you’ve worked in vaccines during the past 10 years, you can take pride in the fact that 26 million of these lives were saved while you were busy completing the daily tasks associated with this life-changing work.
This year, NIIW will be celebrated April 26 to May 3. Take some time to celebrate your work and the families everywhere who remember these diseases because of family members taken from them.
For more information about NIIW or ideas of things you can do to celebrate, check out the CDC’s Web page.
It’s happened again — another celebrity sharing her reasons for not vaccinating her children and offering misinformation in the process. On March 13, when speaking with Lisa Kennedy on Fox show, The Independents, Kristin Cavallari, reality television star and wife of the Chicago Bears quarterback Jay Cutler, admitted that she is concerned enough about vaccines and autism that her son is not vaccinated. The next day she appeared on Fox and Friends where she tried to clarify her position and suggested that it should not matter to other parents, stating “I understand both sides of it. I’ve read too many books about autism and there’s some scary statistics out there. It’s our personal choice, and, you know, if you’re really concerned about your kid get them vaccinated.”
First, knowing about the story will allow you to be prepared. Second, addressing any specific concerns parents bring up with correct information will give you an opportunity to ease their fears:
If you wish to watch the interviews, both are posted on the Fox News website. Scroll to the bottom of the page to see the original interview.
Kristin also mentioned Homefirst as a group that claims no cases of autism in their unvaccinated population. Patricia Callahan and Trine Tsouderos, reporters at the Chicago Tribune wrote a story about this group and its enterprising lead physician, Mayer Eisenstein in 2009, Autism doctor: Troubling record trails doctor treating autism. Selling vitamins and, at one point, his own insurance plans, as well as treating autistic children with Lupron and vitamin D, Eisenstein’s practice was described as having had higher than average malpractice suits and one of the largest wrongful-death verdicts against them in history.
Finally, following up with resources for additional information, including information about how to interpret information in the media, will give parents a sense of validation and an opportunity to find more information if they choose to do so:
Julie Leask and colleagues in Australia published a paper, “Communicating with parents about vaccination: a framework for health professionals,” in BMC Pediatrics in 2012 that recently came to attention and is worth revisiting if you have not seen it or simply need a refresher.
Based on a review of the literature, the researchers describe five groups of parents related to attitudes about vaccination and the relative proportion of parents in each category:
In addition to describing each of these groups, the authors discussed the importance of building a relationship with parents, providing appropriate information and tailoring discussions to the needs of the individual patient or family. Goals and strategies for each group were also discussed and sample dialogues provided.
The article is available for free access courtesy of BioMed Central.
Editor’s note: David Rubin, MD, MSCE and Kathleen Noonan, JD, the co-directors of the PolicyLab at The Children's Hospital of Philadelphia presented Grand Rounds for CHOP staff in January 2014. PolicyLab is a center of emphasis at CHOP focused on health services and health policy research with a mission of “evidence to action.” This article is based on notes taken during the Grand Rounds presentation.
As we begin 2014, several critical components of the Affordable Care Act (ACA) will go into effect raising questions about which changes are taking place and how the landscape of healthcare will change over time. In 2010, when the ACA passed, approximately 50 million people in the United States were uninsured. Most of these people were adults; in fact, at the time of passage, about 90 percent of children had medical coverage, but only about 78 percent of adults did. Further, a large group of uninsured adults were between the ages of 18 and 35 years of age.
According to the Congressional Budget Office, the costs associated with the uninsured were about $43 billion in unreimbursed healthcare charges. In addition, the healthcare industry spent approximately $90 billion dollars in administrative costs associated with underwriting who was eligible for coverage. By 2010, healthcare costs represented about 16 percent of our gross domestic product (GDP) and were increasing.
A main goal of the ACA was to increase coverage thereby decreasing the costs associated with the uninsured, allowing for redirection of funds being spent by insurers and slowing the rate of increase to the GDP.
As written, the ACA would have allowed 32 of the 50 million uninsured persons to enter the insurance marketplace. This would have been accomplished by the implementation of individual mandates, abolition of pre-existing conditions policies, addition of employer penalties for non-coverage of employees and expansion of Medicaid. Two of these have been challenged legally – individual mandates and expansion of Medicaid:
The result of the difference between ACA as written and as implemented after the Supreme Court decision is unintended coverage gaps:
Like any new legislation, implementation of the ACA will not be without hurdles, and modifications to the law are likely. The ACA is, nonetheless, unprecedented in its intention to close the health insurance coverage gap in the United States. Further, the law makes it imperative that healthcare providers focus on providing high-quality, affordable care in a standardized, evidence-based environment. Finally, the law expands the importance of prevention and overall population health and requires providers to plan and provide care through this lens.
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