Greetings, again! We are going to discuss the new vaccinations that are on the horizon for the SARS-CoV-2 virus, the virus that causes COVID 19. The vaccines themselves are a very interesting topic, but how those who are affected by PI may respond to the various mechanisms of the vaccines can be crucial to the PI community.
It’s hard to believe that this quickly into the COVID 19 crisis we are already talking about vaccines that are viable and in advanced testing. There are thirty-seven different vaccines that are in at least phase one testing. There are three vaccines that have not yet completed phase three testing and yet are available and approved for early or limited use. That represents an incredible amount of work having already been completed, and teams of researchers fully engaged in the search for vaccines that will curb this pathogen.
In January, researchers deciphered the SARS-CoV-2 genome. March marked some of the earliest trials to test the safety of vaccines in the human population. Lets look at the development of a vaccine in general for a moment:
There is a phase called Preclinical Testing, when the candidate vaccine is tested on individual cells and given to animal models, such as mice or monkeys. This phase tests whether an adequate immune response is achieved. There are currently at least 91 preclinical vaccines under active investigation.
Phase 1 Safety Trials are conducted using a small population of volunteers to test safety and dosage. These tests also look for an adequate immune response to the vaccine. There are currently 24 vaccines in Phase 1 studies.
Phase 2 Expanded Trials are conducted on hundreds of people divided up into groups. These groups, such as children or the elderly, help to determine if the vaccine acts differently depending on the patient population it is administered to. Researchers continue to evaluate the safety and efficacy of the vaccine. Currently Phase 2 has 14 vaccines active.
Phase 3 Efficacy Trials are conducted using thousands of people. These trials look for infection rates among treated people versus people who receive a placebo. In June the FDA determined that a target of 50% of treated population protected would be considered an effective vaccine. These studies also have enough people to reveal relatively rare side effects that might be missed in smaller populations. There are 9 vaccines in Phase 3.
Early or Limited Approval is a practice that is considered to be seriously risky. These are vaccines that are approved without waiting for the results of Phase 3 trials. So far, only China and Russia have a total of three vaccines that are approved for use without completing Phase 3 trials.
Regulators in each country review the vaccines based on the trials. During a pandemic a vaccine may receive emergency use authorization before getting a formal approval. So far no vaccines have reached the Approved status.
One way to accelerate development is to combine some of these steps. Some coronavirus vaccines now in development are currently in Phase 1/2 trials. As an example, Johnson & Johnson, using a method developed by Beth Israel Deaconess Medical Center in Boston, has a vaccine in Phase 1/2 trials since July and will launch, or perhaps has already launched, a Phase 3 trial in September. This vaccine has a lot of promise and the federal government has agreed to pay one billion dollars for one hundred million doses if the vaccine is approved.
So, all of this is very interesting and exciting, but how is this conversation affected by the introduction of a diagnosis of PI, Primary Immunodeficiency? The hard truth of the matter is that vaccines may be less effective, or even harmful, in immunocompromised patients. This, of course, includes the PI community as well as those who are HIV+ or have an AIDS diagnosis. Live vaccines in particular have been observed to cause problems with immunocompromised patients. In particular, in patients with severe T-cell defects such as SCID, Complete DiGeorge syndrome, NEMO, MHC II deficiency and related disorders live vaccines are strictly contraindicated. In these same populations inactivated vaccines may be ineffective. Also, for B-cell deficiencies, such as X-linked agammaglobulinemia or Common Variable Immunodeficiency, most live vaccines are contraindicated. These populations seem to have some response to influenza vaccine, so it is worth looking at the response to a potential SARS-CoV-2 vaccine. Those with Phagocyte deficiencies, such as Chronic granulomatous disease, leukocyte adhesion deficiency, both live viral and inactivated vaccines are safe and recommended.
Quite possibly, with all the talk about COVID 19 recently, you’ve heard the term “Herd Immunity”. This term is used to describe what happens when a good majority of a population is immunized against or exposed to a pathogen. Each member of the population that is immunized or has been exposed to the pathogen will have a degree of protection against being infected by that pathogen. Herd immunity occurs when the number of people who are protected against the pathogen is so high that transmission of the disease from infected individuals is minimized, so that even those who cannot be protect by immunization, or for whom immunization is less than optimal, can be protected as well as possible from the effects of the pathogen. It is really important for those of us who cannot utilize immunization to encourage our friends and loved ones to be immunized so that the risk of transmission within our close circles is reduced.
Just a reminder here that the author is not an expert in either PI, HIV or COVID 19. I have done a fair amount of research to bring to you information from a layman’s perspective, but it is just that, a layman’s perspective. I would encourage all who have read the above information to look into the details behind the text by using the references to this topic listed below. Good health to all!
- Coronavirus Vaccine Tracker, website, New York Times
- COVID-19 Treatment and Vaccine Tracker, website, Milken Institute
- COVID-19 Video Update, video, Immune Deficiency Foundation
- What is primary immunodeficiency (PI)?, webpage, my Ig source
- Coronavirus (COVID-19), website, Centers for Disease Control and Prevention
- Coronavirus Resource Center, website, Johns Hopkins University & Medicine
- Primary Immune Deficiency Diseases, website, NIH National Institute of Allergy and Infectious Diseases