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)
Page 50:
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.
Page 51:
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….
Page 70:
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?)
Source:
(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
(8) Flumist
(9) Human and Bovine Serotype G8 Rotaviruses
(10) Products Advisory Committee
Comments
2 Comments on Secondary Transmission: The short and sweet about live virus vaccine shedding.
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jules on
Mon, 25th Feb 2008 10:18 am
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Marconi on
Mon, 25th Feb 2008 10:45 pm
I believe the titer test(blood test) for Measles can also tell if it was the vaccine-type Measles or wild Measles. Someone feel free to correct me if I am wrong:)
Some people never develop an immunity-vaccinated or not. That is why some people get chicken pox more than once, or some women get repeated Rubella vaccines and still show no immunity. Reinfection is also always ‘possible’ if vaccine or natural immunity wears off over time due to NOT being exposed which helps keep immunity level up.
The titre blood test cannot differentiate between vaccine-type measles or wild measles. In order to do that, the virus would have to be typed with a test called Polymerase Chain Reaction, and the “bar code” compared with the reference viruses for either the vaccine virus, or the wild virus. Furthermore, the vaccine virus varies slightly with every new attenuation, so each batch of vaccine might show a slight genetic variation from each other.
To say some people never develop immunity, vaccinated or not is very simplistic. If you mean, some people never show antibodies on a titre test, that too is very simplistic. The current titre test offered to parents is a crude measure. Using other tests such as ELISA, antibodies can be picked up, which the standard titre test does not.
It is “normal” for some people to develop antibodies, for antibotides to subside over time, and for a titre test years later to show no antibodies. However, if you vaccinated those people, or blood tested them before and after a known exposure and subclinical infection during with the person shows no signs of infection, the immediate rise in detectable antibodies over a period of days is a specific curve which shows an anamnestic response. What that means is that the person actually did have immunity, but it was “memory” immunity. Just because a person doesn’t have “detectable” immunity according to a titre test, doesn’t mean they have lost their immunity.
What it means is that immunologists have not yet devised a method for detecting permanent “memory” immunity.
Virology texts are also interesting, in that they point out that many children who don’t have antibodies cope very well with diseases like measles. The reason for that is that the key to survival of a first exposure to disease in any person, isn’t antibodies anyway. When you first come in contact with any disease, how well you survive that is due to your “cellular” immune system, which does utilise IgA, and IgM at some point if you have a normal immune system. But most textbooks, even older ones by ‘greats’ like McFarlane Burnett, describe in great detail, children who have no antibodies, who cruise through measles and polio. The rate of paralytic polio in normal children (using the most virulent strain as a reference point) is one case of paralysis, per 100 children with mild symptoms. The historical rate of paralysis in children with no antibodies is 6 per 100. So while children with no antibodies are 6 times more likely to get paralytic polio, the cellular immune system of those children guarantees that 94 out of 100 of them will not.
Yes, some children with no antibodies will get sick and die. But not all of them will.
The key to fighting an infection for the first time, in everyone, normal or not, is a well functioning cellular immunity is nutrition, nutrition, and nutrition. A person can have a normal immune system, but if they have malnutrition or bad nutrition, their immune system will not work properly, and they can die regardless. Anyone working in Africa can tell you that. The connection between nutrition, infection and immunity has been, and is very strong in the medical literature.
A huge amount of “immunity” is based on the integrity of the gastro-intestinal system, and the person’s nutritional status. Antibodies are essential the net at the bottom of the cliff, which while vital, isn’t the most important factors.
Using Tetanus as an example, were antibodies the most important part of the immune system with regard to protection against tetanus, then the human beings on the earth would never have got past the first generation. Even in the western world, civilians had no access to a tetanus vaccine until around 1960 (at least in the country in which I live). You just have to look at your own family tree to realise that your great great grandparents probably died of other things rather than tetanus during childhood.
So the use of antibodies as a measuring rod of “immunity” is not only a very crude measure, it’s inaccurate. But it’s a very useful “weapon” with which to create fear.
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