Secondary Transmission: The short and sweet about live virus vaccine shedding.
A child gets vaccinated and is from that moment on protected from the vaccine virus, correct? We all realize that vaccines are not 100% failproof, but is that the only concern?
If it only were that simple. The fact is that once a child is injected with a live virus vaccine (and let’s assume that this child is immune as a result of it) there are still other things to consider which most parents do not know about and most pediatricians fail to warn about – which is vaccine shedding!
Shedding is when the live virus that is injected via vaccine, moves through the human body and comes back out in the feces, droplets from the nose, or saliva from the mouth. Anyone who takes care of the child could potentially contract the disease for some time after that child has received certain live vaccines. This was a huge problem with the oral polio vaccine, and was one of the reasons why it was taken off the market in the US.
The OPV is still used in developing counties.
Secondary transmission happens fairly often with some of the live virus vaccines. Influenza, varicella, and Oral Polio Vaccine (OPV) are the most common. On the other hand it may happen very seldom or not ever with the measles and mumps vaccine viruses.
Here are the vaccines that shed or have been known to result in secondary transmission:
Measles Vaccine – Although secondary transmission of the vaccine virus has never been documented, measles virus RNA has been detected in the urine of the vaccinees as early as 1 day or as late as 14 days after vaccination. (1)
In France, measles virus was isolated in a throat swab of a recently vaccinated child 4 days after fever onset. The virus was then further genetically characterised as a vaccine-type virus. (2)
Rubella Vaccine – Excretion of small amounts of live attenuated rubella virus from the nose and throat has occurred in the majority of susceptible individuals 7-28 days after vaccination. Transmission of the vaccine virus via breast milk has been documented. (3)
Chicken Pox Vaccine – Vaccine-strain chickenpox has been found replicating in the lung (4) and documented as transmtting via zoster (shingles sores) (5) as well as “classic” chickenpox (6) rash post-vaccination.
Oral Polio Vaccine (OPV) – In areas of the world where OPV is still used, children who have been vaccinated with it pass the virus into the water supply through the oral/feces route. Other children who then play in or drink that water pick up the vaccine viruses, which can pass from person to person and spark new outbreaks of polio. (7) *
FluMist Vaccine – The mist contains live attenuated influenza viruses that must infect and replicate in cells lining the nasopharynx of the recipient to induce immunity. Vaccine viruses capable of infection and replication can be cultured from nasal secretions obtained from vaccine recipients.
Transmission of a vaccine virus from a FluMist recipient to a contact was documented in a pre-licensing trial. The contact had a mild symptomatic Type B virus infection confirmed as a FluMist vaccine virus. (8)
Rotavirus Vaccine (RotaTeq) – There is a possibility that one strain of rotavirus which is presently circulating may be an “escaped” vaccine strain, from an old Finnish rotavirus vaccine. (9)
Following are excerpts from the discussion by the FDA Advisory Committee on RotaTeq vaccine shedding: (10)
The latest shedding that we saw was 15 days from dose one.
We had no subjects that shed after dose two, and only one subject shed after dose three. He shed four days from dose three.
A: The quantities were low, similar to what we saw in phase 2 studies, as well.
We also had two placebo recipients that shed, and of course, this raised a red flag for us.
B: Could this have been transmission of vaccine virus from vaccine recipients to placebo recipients?
A: We did a very thorough investigation looking for opportunities for a vaccine transmission to occur and did not find anything. These children were not siblings of a vaccine recipient. They didn’t attend day care with vaccine recipients. They didn’t have a common caretaker with the vaccine recipient, and in the office and clinic in which they were vaccinated, they were not exposed to vaccine recipients.
So going on then to summarize general safety, Rotateq was well tolerated….
Question and answer section –
Then with respect to the possibilities of how these children ended up with vaccine strains in their stool, we really could not find the answer for that. We even went so far as to look and see like on the day that that child was in the clinic, were other children getting vaccine, you know, right before or after them?
And that was not the case. So it has been a puzzle, and we don’t have an answer as to why these children had vaccine strains in their stool.
(One has to ask: Could the reason have been that someone mixed up the placebo with the actual vaccine vials and consequently some kids of the control group got the real vaccine?)
(1) Detection of Measles RNA
(2) Detection of measles vaccine in the throat of a vaccinated child.
(3) MMR II
(4) Vaccine Oka Varicella-Zoster Virus
(5) Chickenpox Attributable to a Vaccine Virus
(6) Genetic Profile of an Oka Varicella Vaccine Virus
(7) Polio Outbreak in Nigeria
(9) Human and Bovine Serotype G8 Rotaviruses
(10) Products Advisory Committee
*We have had complaints (see comments) that we quote-mined reference (7). Here is the complete quote from the article.
“Other children who then play in or drink that water pick up the vaccine’s virus, which gives them some protection against polio. But in very rare instances, as the virus passes through unimmunized children, it can mutate into a form that is dangerous enough to spark new outbreaks.”
There is a long-running mystery about polio and something called Acute Flaccid Paralysis, which is not polio, but which seems to increase as polio decreases. There is no direct link to the polio vaccine, but some researchers have found that more doses of oral vaccine are linked with high rates of AFP.
“It is sad that, even after meticulous surveillance, this large excess in the incidence of paralysis was not investigated as a possible signal.”
nor was any effort made to try and study the mechanism for this spurt in non-polio AFP.”
Please read all of the comments below and let us know if you think there is some quote-mining going on. Thanks!