- A case of diphtheria has been confirmed in an elementary school in Edmonton, Alberta, Canada.
- Three other people, who are asymptomatic carriers of the bacterial disease have been identified and are being treated in isolation.
- The diphtheria vaccine is only available as a combination vaccine (DT, Td, DTaP, Tdap) and its effectiveness wanes over time.
A rare case of diphtheria was identified at an elementary school in Edmonton, Alberta, Canada—the third case in that school district since 2017.1 Public health officials subsequently identified three other people, who are asymptomatic carriers of the bacterial disease and are being treated in isolation. The Alberta Health Services (AHS) is monitoring and treating the patient, carriers and all potential contacts.
According to the AHS, “People who have been fully vaccinated, or immunized for their age, can become carriers when they come into contact with the bacteria that causes diphtheria. They often don’t show symptoms.” To protect them, as well as those they may come into contact with, those asymptomatic carriers are being treated and “are subject to the same isolation protocols as someone who is identified as symptomatic.”2
Fully Vaccinated Asymptomatic Carriers of Infection
Diphtheria is not, by any means, the only infection that may be transmitted by fully vaccinated, asymptomatic carriers. Pertussis, measles, polio and influenza are among the infections that have been implicated in transmission of infective pathogens from asymptomatic, vaccinated hosts.
According to the Centers for Disease Control and Prevention (CDC), “Acellular pertussis vaccines may not prevent colonization (carrying the bacteria in your body without getting sick) or spread of the bacteria.”3 Evidence shows that pertussis—including new strains that have adapted to evade the vaccines—may be carried and transmitted by fully vaccinated individuals who are infected but express no symptoms of disease.4 5 Two referenced reports published by the National Vaccine Information Center in 2016 and 2018, provided evidence for the fact that children and adults who have received whole cell pertussis vaccines (DPT) and acellular pertussis vaccines (DTaP, Tdap) are capable of being infected with and transmitting pertussis without showing any symptoms and that the pertussis microbe has also evolved to evade the vaccines.6 7
In 1973, it was recognized that the live attenuated virus measles vaccine did not always prevent infection with wild type measles, and public health officials also were “not sure about whether some vaccinated children could still transmit wild type measles to others.”8 Even the attenuated (weakened) MMR vaccine used today does not always prevent wild strain measles virus from infecting and being transmitted by asymptomatic, vaccinated carriers, whose cases are never identified or reported like cases of measles in unvaccinated children and adults fully displaying symptoms of measles. It is a little known fact that the MMR vaccine can suppress symptomatic expression of disease but fail to block transmission of the infection to susceptible individuals. In fact, it has been suggested that when it comes to measles outbreaks, “Most transmissions in highly vaccinated populations are from the vaccinated, asymptomatic carriers with subclinical infections.”9
It is the same story with poliovirus infection. Noting that the live attenuated polio vaccine (OPV), which is not used in the U.S. anymore but is used in other countries, does not prevent asymptomatic infection and further spreading of polioviruses. In a 2018 report, the CDC warned of several possible scenarios.
For example, “a vaccinated worker could still become infected, or re-infected, while working with poliovirus and shed live virus for weeks, leading to possible infection of others.” The CDC report also suggests, “A person who has an asymptomatic poliovirus infection could travel to a place where vaccine coverage is low. Shedding of virus in that setting could potentially result in re-introduction to a susceptible population, further transmission and cause polio disease.”10
The invisible threat of disease transmission by fully vaccinated, asymptomatic carriers of infection is important to recognize given the potentially serious nature of some of these diseases and the fact that often unvaccinated persons are blamed for causing disease outbreaks when there are undiagnosed and unreported cases occurring in fully vaccinated persons.
Characteristics of Diphtheria
Diphtheria is a highly contagious bacterial infection that may seem at first like any other upper respiratory tract infection. In all but the mildest cases, however, the disease progresses to produce a toxin that invades the lining of the respiratory tract and attacks healthy tissue. The dead tissue accumulates as a thick, gray, green or blackish web-like coating of the nose, tonsils, voice box, and throat that can make it difficult to breathe or swallow.
The toxin can also enter the bloodstream and cause damage to the heart, nerves, kidneys and brain.11 Diphtheria occurs less in a “cutaneous form,” as a skin infection characterized by painful lesions that may be covered by the signature gray membrane. The cutaneous form of diphtheria is most often seen in tropical climates but may develop anywhere there are non-hygienic, crowded conditions.12
The disease is spread most commonly through direct contact with saliva or respiratory droplets, as through coughing or sneezing, which may spread the disease efficiently in crowded conditions. It also may be transmitted via contaminated personal items such as used tissues or unwashed drinking glasses or, rarely, through contact with toys or clothing used by infected people. Diphtheria may also spread from someone who carries the bacteria, but has no symptoms for it, as may occur when a vaccinated individual picks up the bacteria but does not show symptoms.13
Vaccination against diphtheria is only available as part of a combination vaccine that also includes vaccines against tetanus (TD) or tetanus and pertussis (whooping cough) (DTaP). The combination vaccines are typically given to children in the United States at two, four, six and 15-18 months and between four and six years. Boosters are recommended every 10 years thereafter.14
It is generally recognized that much of the reactivity of DTaP/Tdap vaccines, including injuries and deaths, is caused by the pertussis component of the combination shots. However, it is not possible to get diphtheria vaccine alone without also being injected with either tetanus vaccine or, more often, both tetanus and pertussis vaccines combined with diphtheria vaccine.15
As of July 31, 2018, MedAlerts data show that, since 1990, more than 174,000 adverse reactions, hospitalizations, injuries and deaths were reported to the federal Vaccine Adverse Events Reporting System (VAERS) following one of the combination vaccines that includes diphtheria.16 Those adverse events have included 2,992 related deaths, 20,106 hospitalizations, and 2,946 related disabilities, the majority among children under age six. In the federal Vaccine Injury Compensation Program (VICP), a total of 5,514 claims had been filed prior to November 28, 2017 for injuries and deaths following vaccination with DTaP or Tdap. That number included 84 deaths and 4,660 serious injuries.17
Like most vaccines, the effectiveness of the diphtheria vaccine is known to wane over time. The CDC recommends booster doses of Td (tetanus-diphtheria) vaccine every 10 years. Unlike many infectious diseases, even natural infection with diphtheria does not confer life-long protection. People can have diphtheria more than once.
The prognosis for diphtheria has changed little over the past 50 years, despite improvements in treatment options: Between 5-10 percent of cases are fatal, and mortality may reach 20 percent for those under age five or over age 40. In past centuries, before the development of antibiotics and an antitoxin, the death rate for diphtheria was closer to 50 percent.
The risk of acquiring diphtheria infection in the U.S. or other developed countries is extremely remote, unless traveling to “an impoverished country or a location of a natural disaster that has compromised the sanitation infrastructure.”18 There were only two reported cases in this country between 2004 and 2016. The disease, however, continues to present a challenge in other parts of the world, with over 7,000 cases reported to the World Health Organization (WHO) in 2016 alone.19
1 Omstead J. Rare Infection Confirmed At Edmonton Elementary School. CBC News June 9, 2019.
2 3 Carriers Identified After Confirmed Case Of Diphtheria At Edmonton School. CBC News June 13, 2019.
3 Centers for Disease Control and Prevention. Pertussis Frequently Asked Questions. CDC.gov Apr. 1, 2019
4 La Vigne P. Symptom-Free Vaccinated Individuals May Be Spreading Pertussis. The Vaccine Reaction July 14, 2016.
5 Althouse BM and Scarpino SV. Asymptomatic transmission and the resurgence of Bordetella pertussis. BioMed Centra 2015.
6 Fisher BL. Pertussis Microbe Evades the Vaccines as Experts Argue About Why. NVIC Newsletter Mar. 27, 2016.
7 Fisher BL. The Pertussis Vaccine Blame Game. NVIC Newsletter Sept. 12, 2018.
8 Fisher BL. What Is Going On With Measles? The Science and Politics of Eradicating Measles. NVIC Newsletter May 25, 2019.
9 Weiler JL. What is Driving Preventable Disease Outbreaks? Cures Feb. 21, 2019
10 U.S. National Authority for Containment of Poliovirus. The Need for Containment. CDC.gov Oct. 15, 2018.
11 Diphtheria. MedlinePlus Dec. 13, 2017.
12 Diphtheria. Mayo Clinic May 16, 2018.
13 Diphtheria. National Vaccine Information Center 2019.
14 See Footnote 10.
15 NVIC. Can Pertussis Vaccine Cause Injury and Death? NVIC.org. 2019.
16 NVIC. MedAlerts Search Results. NVIC.org 2019.
17 See Footnote 11.
19 CDC. Diphtheria. CDC.gov Feb. 26, 2019.