Meryl Nass, MD
First written in May 2015, updated in February 2019
In April-May 2015 there were multiple news articles, and testimonies in the Maine and Vermont legislatures, about the need to impose vaccine mandates to protect immunocompromised children.  I attended the vaccine bills' hearing in Augusta, Maine on May 11, which lasted into the night. I also attended the Vermont Senate hearing 3 weeks earlier. The Vermont Senate committee said it would only hear testimony from physicians, which is why I was invited. Not very many doctors are familiar with the vaccine literature. Vaccines are, surprisingly, an arcane area of medicine.
Unfortunately, I heard not a single expert (at either hearing) provide any data about the magnitude of the problem that vaccine mandates are supposed to fix. In fact, I was quite surprised to learn that danger to the immunocompromised seemed to be the major justification to remove vaccine exemptions. I heard no one mention the fact that vaccine efficacies of 40%, 60%, 80% (approximately correct for influenza, diphtheria, mumps vaccines--check these links!) might also pose some risk to the immunocompromised. (These are examples; most other vaccines have efficacy in the 60-95% range.) Actually, common sense tells you that vaccine failure rates of 60%, 40% and 20% pose considerably more risk of spreading infection than exemption rates under 5% in Maine. Low vaccine efficacy rates make the idea that we can protect the immunocompromised by ending vaccine exemptions a sad joke--but did even one "expert" at the hearings admit it?
How much risk is actually posed by “vaccine-preventable” diseases to the immunocompromised? I reviewed the most common infections seen in those at highest risk: stem cell (bone marrow) transplant recipients and leukemia patients. Patients with solid organ transplants and those under immunosuppressive treatment for autoimmune disorders are at risk for generally the same infections.
It turns out that the great majority of dangerous infections that immunocompromised people develop cannot be prevented by vaccines, because we do not have vaccines for most of them. Which is probably why you have never heard of most of them.
Here a 2013 review lists the problem viruses:
"The limited data show that community acquired respiratory viruses (CARVs) and herpesviruses are the most common pathogens. Among the causes of CARV respiratory tract infections, a preponderance of respiratory syncytial virus (RSV) and parainfluenza virus (PIV) are reported, followed by influenza virus and human metapneumovirus (HMPV). In the herpesvirus family, the incidence of herpes simplex virus (HSV) and varicella zoster virus (VZV) infections as well as cytomegalovirus (CMV) diseases have significantly decreased because of effective prophylaxis." [Due to using the drug acyclovir--Nass] "The reports on human herpes virus (HHV)-6 diseases are increasing.
... Other viruses, such as herpesviruses and adenovirus, may also result in respiratory infections... Herpesvirus pneumonia is usually caused by reactivation of latent viruses which occurs in severe immunosuppression.
... viral encephalitis was mainly caused by human herpes virus (HHV)-6, followed by Epstein-Barr virus, Herpes Simplex virus, JC virus, Cytomegalovirus, Varicella Zoster virus in the recipients of allogeneic-Hematopoietic Stem Cell Transplantation. Our data showed that herpesvirus-associated encephalitis was mainly caused by EBV followed by HSV, CMV and VZV.
... The most frequent pathogens of viral hepatitis are hepatitis B virus (HBV) and hepatitis C virus (HCV). Besides these, other viruses such as CMV and HSV may also result in hepatitis. Hepatitis B and C can be caused by either virus reactivation or blood transmission..." [Not by spread between children--Nass]
There are also many bacterial and fungal infections that can occur. There are no vaccines for fungal infections. Pneumococcal vaccine may provide a small benefit against limited serotypes of one bacterium. Other bacterial vaccines do not protect against pathogens common in the immunocompromised.
Of the viral infections immunocompromised patients commonly develop, the only three for which there exists a vaccine, and which may be spread by casual contact, are influenza, chickenpox and rotavirus. Rotavirus is a mild gastrointestinal virus -- even in those with impaired immunity, mortality is rare.
Influenza is a concern, but influenza vaccines are notoriously ineffective. During the 2014-2015 flu season, CDC said the flu vaccine had 19% efficacy. (A Canadian study found no efficacy for that year's flu vaccine.) Over the past 14 years, CDC’s efficacy estimates for influenza vaccines averaged 40%. So even if everyone in America was vaccinated, you could never generate herd immunity for influenza. You could not achieve the desired "cocoon" for those most vulnerable.
Influenza vaccine is not a live vaccine, and (like a number of other vaccines) is actually recommended for most immunocompromised patients by the Infectious Diseases Society of America. In an NIH study of immunocompromised patients with influenza, however, only 25% had been vaccinated for influenza.. It may be that the immunocompromised are mistakenly omitting vaccinations likely to protect them. However, the poor efficacy of influenza vaccines can provide only limited benefit. The NIH study concluded, "The immunocompromised patients are at risk of more severe or complicated [influenza] disease, which may be difficult to prevent with current vaccines and treat with current antivirals."
Chickenpox (Varicella zoster virus/VZV) is caused by a virus that, once you have been infected, will live forever in your nerve cells. The vaccine virus also does this. Immunocompromised patients developing chickenpox/VZV infections are usually reactivating latent virus long present in their own bodies. Only occasionally are they “catching” chickenpox virus from someone else.
In a study of children who had undergone stem cell (bone marrow) transplants, 76% of varicella infections were due to reactivation of viruses already resident in their bodies. Furthermore, none occurred in patients receiving the antiviral drug acyclovir. Varicella infections in the immunocompromised are effectively prevented and treated with acyclovir. If that isn't adequate, varicella immune globulin can be used. In this study, no patient who developed a varicella infection after their transplant died.
Let me reiterate: vulnerable, immunocompromised children are susceptible to many viral, bacterial and fungal infections, but these are only rarely caused by child to child spread of microorganisms for which we have vaccines. These infections are described in footnotes 3 and 4. For most infections immunocompromised children may acquire, no vaccines exist.
It is troubling that vulnerable families have been encouraged to fear and stigmatize unvaccinated children, when the percentage of children with primary vaccine failure (the vaccine never "took") and secondary vaccine failure (vaccine-induced immunity disappeared over time) are far greater than the percentage of children lacking vaccinations. [CDC's 2012-13 kindergarten vaccine exemption rates by state ranged from a low of 0.1% to a high of 6.5%.]
The number of vaccinated people who lack immunity to a "vaccine-preventable disease" despite their vaccinations is large. Whether someone who has been vaccinated is likely to be immune depends on the type of vaccine, the person, and the time that has elapsed since vaccination. There are far more vaccinated but non-immune children in school than those without vaccinations. As I noted at the beginning of this article, unsatisfactory vaccine efficacies of 40%, 60%, and 80% (for influenza, diphtheria, mumps vaccines) should pose far more risk to the immunocompromised than vaccine exemption rates of 1-5%.
If unvaccinated children are to be denied schooling to protect the immunocompromised, shouldn't we be testing all schoolchildren to be sure they are actually immune? Should those lacking immunity despite their vaccinations be sent home too?
If fragile, immunocompromised children are not being harmed by vaccinated classmates who lack immunity (vaccine failures), then it stands to reason they are not suffering from exposure to the unvaccinated, either. Don’t vulnerable families have enough real problems, without adding unfounded and unjustified fears? Isn't it time to drop this canard?
As I wrote in a letter published by the BMJ (formerly British Medical Journal) in January 2019, there have been only 3 deaths in the past 20 years, in the entire United States, associated with measles. Only one death in 20 years occurred in a child, in 2003: a 13 year old boy who had received a bone marrow transplant 3 months earlier, who lacked any identified exposure to a measles case. It is unclear if he died from a vaccine-strain measles virus (perhaps long resident in his gut) or a wild-type measles virus.
We need to know if vulnerable, immunocompromised children are truly catching and dying from vaccine-preventable diseases, and if so, from whom they are catching these diseases: from the vaccinated, from the unvaccinated, or from their own latent viruses? From vaccine strains or wild-type (natural) infections? How many children are affected? Which diseases are maiming or killing them? Where is the evidence?
Before we "fix" this elusive problem by attacking vaccine exemptions, can someone describe the dimensions of the problem? Does this problem actually exist?
 Portland Press Herald http://www.pressherald.com/2015/05/10/a-maine-teen-has-to-ask-is-everyone-in-this-room-vaccinated/
 Vermont Public Radio http://digital.vpr.net/post/passions-flare-hearing-proposal-eliminate-philosophical-exemption