Community immunity is the new “herd immunity.”
The CDC defines community immunity as “[a] situation in which a sufficient proportion of a population is immune to an infectious disease (through vaccination and/or prior illness) to make its spread from person to person unlikely. Even individuals not vaccinated (such as newborns and those with chronic illnesses) are offered some protection because the disease has little opportunity to spread within the community. Also known as herd immunity.”
Does the term apply to all vaccines? Let’s examine.
For a vaccine to be able to create and sustain community immunity, it must be able to prevent not only the symptoms of disease but also the transmission of a communicable infection, and an individual’s vaccine protection from the targeted infection must not wane away.
Does being vaccinated for the flu prevent you from spreading influenza virus? No.
- A 2013 study published in Clinical Infectious Diseases reported finding “no evidence that vaccination prevented household transmission once influenza was introduced.”
- The 2016 Cochrane Review concluded that “[o]ffering influenza vaccination to HCWs [healthcare workers] based in long term care homes may have little or no effect on the number of residents who develop laboratory-proven influenza compared with those living in care homes where no vaccination is offered.”
- A study published in Scandinavian Journal of Immunology in 2004 states: “The absence of immune response [to vaccination] in the nasal mucosa may indicate a lack of appropriate local influenza virus stimulation. An apparent drawback to traditional parenteral [i.e., intramuscular] vaccines is that they induce a weak and short-lived local mucosal immune response.” In other words, flu shots do not generate protective antibodies in the nasal mucosa, which harbors the flu virus upon infection along with the lower respiratory tract, where it causes more severe symptoms. So, even in case when the flu shot may protect you from the flu symptoms caused by vaccine-matching strains, you are still able to carry them in your nasal mucosa and spread them.
- You don’t have to rely upon the respiratory symptoms (sneezing and coughing) to spread the flu virus — aerosol shedding will suffice. And if you get the flu despite being vaccinated, you will be shedding the flu virus at increased rates, per this 2017 study published in PNAS. “We observed 6.3 (95% CI 1.9–21.5) times more aerosol shedding among cases with vaccination in the current and previous season compared with having no vaccination in those two seasons.”
Does being vaccinated for pertussis prevent you from spreading it? No.
The acellular pertussis (aP) vaccine may transiently prevent the symptoms of whooping cough, if you are recently vaccinated. But if exposed to pertussis, you will still be colonized with the bacteria (Bordetella pertussis), per this study conducted by the FDA researchers and published in PNAS in 2014. You may have no symptoms at all, or symptoms that feel like common cold, and so you wouldn’t realize you may be spreading pertussis, which would be dangerous to do around infants.
Does being vaccinated for mumps in your childhood prevent you from getting it during an outbreak? No.
There are several problems associated with the mumps portion of the MMR [measles, mumps, rubella] vaccine, the only available mumps-containing vaccine formulation produced by Merck and recommended by the CDC as a 2-dose series on the childhood schedule.
First, two of the Merck’s own virologists have taken Merck to court for alleged falsification of the efficacy data on the mumps portion of the MMR. You can read more about the lawsuit HERE.
Second, whatever the true level of the Merck’s mumps vaccine efficacy might be, even that protection wears off over time. The vaccine failure rate increases with the passage of time after the last vaccine. For example, it was reported in a 2017 study of a mumps outbreak published in The New England Journal of Medicine that “[t]he vaccine effectiveness of two doses versus no doses was lower among students with more distant receipt of the second vaccine dose.” Hence, vaccination of young children against mumps simply pushes the risk of disease into adolescence and adulthood. So, even if you are already fully vaccinated, the CDC wants you to get yet another MMR during any outbreak of mumps, instead of relying on nebulous community immunity.
Finally, a 2013 study in Human Vaccine Immunotherapy examined mumps transmission during an outbreak affecting 9th-12th grade students in private Jewish schools with vaccination coverage between 90-100% and found that “mumps transmission requires close contact, and these environmental factors may have overwhelmed vaccine-mediated protection increasing the likelihood of vaccine failure.”
Does the concept of ‘community immunity’ apply to tetanus or diphtheria?
Tetanus is not contagious, meaning it does not spread from person to person. The concept of community immunity for tetanus is as absurd as the concept of community immunity for strokes.
Whereas diphtheria is contagious, the disease is due to the diphtheria toxin secreted by C. diphtheriae bacteria colonizing the throat. The vaccine for diphtheria (a component of DTaP) is simply a formaldehyde-treated inactivated diphtheria toxin, called toxoid. Vaccination with a toxoid is meant to induce antibodies that recognize the toxin, but not the bacteria from which it is secreted. Therefore, toxoid-induced antibodies can neutralize the diphtheria toxin and protect you from toxin-mediated symptoms of disease upon exposure to diphtheria, but they cannot prevent throat colonization by C. diphtheriae and its transmission.
Indeed, a study published in American Journal of Diseases of Children found that C. diphtheriae carriage occurred at the same rate in vaccinated and unvaccinated students during an outbreak in Texas in 1972. The authors of the study also pointed out that “diphtheria outbreaks have been described in populations with as much as 94% of the people being previously immunized. These outbreaks, the known importance of carriers in the spread of diphtheria, and the demonstrated failure of toxoid to prevent the carrier state lead us to conclude that the concept of herd immunity is not applicable in the prevention of diphtheria. A high level of community immunization will not stop the transmission of diphtheria…”
It is known that public health measures to control diphtheria include quarantining any known C. diphtheriae carrier and using antibiotics to eliminate their carriage, even if the carrier doesn’t show the symptoms of clinical diphtheria. These measures, and not vaccination, stop the transmission of C. diphtheriae microorganism between people.
Thus, the concept of community immunity is not applicable to toxoid vaccines, such as those for tetanus or diphtheria.
What about polio?
Does infection with a poliovirus invariably lead to paralytic poliomyelitis? No.
According to the Sanofi Pasteur’s IPOL vaccine insert, “[a]pproximately 90% to 95% of poliovirus infections are asymptomatic. Nonspecific illness with low-grade fever and sore throat (minor illness) occurs in 4% to 8% of infections. Aseptic meningitis occurs in 1% to 5% of patients a few days after the minor illness has resolved. Rapid onset of asymmetric acute flaccid paralysis occurs in 0.1% to 2% of infections, and residual paralytic disease involving motor neurons (paralytic poliomyelitis) occurs in approximately 1 per 1,000 infections.”
This means that 99.9% of polio infections do not result in paralytic poliomyelitis.
Does inactivated polio vaccine [IPV] establish community immunity? No.
Unlike the oral polio vaccine [OPV], which has long been discontinued in the USA, IPV is given via intramuscular injection and does not induce mucosal antibodies in the gastro-intestinal tract, but only stimulates production of antibodies in blood circulation. Immunization with IPV didn’t prevent gut colonization by even attenuated strains of poliovirus, nor did it prevent infected IPV-immunized children from excreting poliovirus in the stool in a 2007 Cuban study published in The New England Journal of Medicine. A 2012 systematic review published in PLoS Pathogens confirms that “IPV provided no protection against shedding [in stool samples] compared with unvaccinated individuals… There were insufficient studies of nasopharyngeal shedding to draw a conclusion.”
It is understandable why the use of IPV in populations with poor sanitation is not considered to be capable of preventing wild poliovirus transmission. From the WHO March 2016 Weekly Epidemiological Record (WER): “IPV is less effective than OPV in inducing intestinal mucosal immunity in previously unvaccinated individuals… Differences… may be illustrated by the persistent circulation of WPV [wild poliovirus] in Israel in 2013, suggesting that WPV transmission can be sustained for months if undetected in areas with high IPV coverage where local factors facilitate transmission.”
Can measles vaccination ensure community immunity and prevent an outbreak? No.
The inability to ensure community immunity from communicable infections is not restricted to just the flu shot, DTaP, or IPV. No vaccine is capable of providing full protection from infection and its spread, especially in extended periods of close-quarter settings, not even the highly-praised measles vaccine. A 1998 study in American Journal of Epidemiology documenting rampant measles transmission in a crowded classroom of highly vaccinated students concluded that “total protection against measles might not be achievable, even among re-vaccinees, when children are confronted with intense exposure to measles virus.”
Vaccination campaigns aimed at disease eradication are sometimes thwarted by the ability of certain bacteria (e.g. non-type b H. influenzae, PRN- B. pertussis) to overcome vaccine-induced selective pressure — such that when a vaccine-targeted strain is nearly eradicated, other strains expand and cause clinically similar disease — resulting in no net benefit in overall disease reduction: a whack-a-mole effort.
Vaccines come with limitations in their utility and with risks each individual must weigh against limited, often short-lasting, personal protection. True community protection from all communicable infections, not just those few the industry has developed vaccines for, is not complicated. Everyone can act responsibly for the benefit of their community by following tried-and-true methods: washing hands often, covering coughs and sneezes, staying home when sick, and making lifestyle changes that support our own natural resilience to sickness.
© Informed Choice WA 2018. All rights reserved. Contributing authors: Bernadette Pajer and Tetyana Obukhanych, PhD
For a more detailed exploration of herd immunity to measles, please read this article: HERD IMMUNITY: CAN MASS VACCINATION ACHIEVE IT? by Tetyana Obukhanych, PhD
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CDC’s Tetanus page. http://www.cdc.gov/tetanus/about/index.html
Miller et al. “Diphtheria immunization. Effect upon carriers and the control of outbreaks.” Am J Dis Child 1972; 123(3):197-9. www.ncbi.nlm.nih.gov/pubmed/5026197
Sanofi Pasteur’s IPOL vaccine insert. http://www.fda.gov/downloads/BiologicsBloodVaccines/Vaccines/ApprovedProducts/UCM133479.pdf
Cuba IPV Study Collaborative Group. “Randomized, placebo-controlled trial of inactivated poliovirus vaccine in Cuba.” N Engl J Med 2007; 356(15):1536-44. www.ncbi.nlm.nih.gov/pubmed/17429085
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WHO March 2016 WER. http://www.who.int/wer/2016/wer9112.pdf?ua=1
Paunio et al. “Explosive school-based measles outbreak: intense exposure may have resulted in high risk, even among revaccinees.” Am J Epidemiol 1998; 148(11):1103-10. www.ncbi.nlm.nih.gov/pubmed/9850133
Tetyana Obukhanych, Ph.D. “HERD IMMUNITY: CAN MASS VACCINATION ACHIEVE IT?” http://www.tetyanaobukhanych.com/herd_immunity.html