# Do vaccines prevent retransmission? **URL:** \ **Category:** Factual Questions\ **Created:** [July 10, 2013, 12:01am UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089 "2013-07-10T00:01:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [July 10, 2013, 12:01am UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/1 "2013-07-10T00:01:16Z")
Let’s say John is vaccinated against Disease XYZ. He catches it anyway but he’s fine because he’s vaccinated. But can John still pass XYZ onto somebody else? ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [July 10, 2013, 12:17am UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/2 "2013-07-10T00:17:27Z")
Generally speaking (and, as with any statement in biology, there are a host of exceptions), an effective vaccination prevents the subject from being infected at all. You’re suggesting a state where the person is infected but without symptoms. That’s pretty rare. Generally, if you get infected, you have the disease; if you don’t have the disease, you’re not infected with the microbe. Obviously, if you’re not carrying the microbe, you can’t pass it to other people. ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [July 10, 2013, 12:52am UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/3 "2013-07-10T00:52:55Z")
In childhood (and I don’t know how accurate this is), I was taught that vaccinations work by priming the immune system to recognize that specific microbe and successfully attack it before a full-blown infection occurs. Doesn’t that mean there’s a period of time when the microbe is in your body and your immune system is busy fighting it off? And during that time, could you transmit it to non-vaccinated others if it’s still in your bloodstream? ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [July 10, 2013, 2:07am UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/4 "2013-07-10T02:07:27Z")
> [@Reply](#): > > Let’s say John is vaccinated against Disease XYZ. He catches it anyway but he’s fine because he’s vaccinated. But can John still pass XYZ onto somebody else? The bottom line is that this can occur if live virus vaccines are given, it’s unusual but not unheard of. _“Most vaccines, including live vaccines (MMR, varicella, zoster, rotavirus, LAIV, and yellow fever) can be administered to infants or children who are household contacts of pregnant or immunosuppressed persons, as well as to breastfeeding infants (where applicable)…Live attenuated influenza vaccine should not be administered to persons who have contact with severely immunosuppressed persons who are hospitalized and require care in a protected environment (i.e., who are in isolation because of immunosuppression). LAIV may be administered to contacts of persons with lesser degrees of immunosuppression. Measles and mumps vaccine viruses produce a noncommunicable infection and are not transmitted to household contacts. Rubella vaccine virus has been shown to be shed in human milk, but transmission to an infant has rarely been documented. Transmission of varicella vaccine virus is not common, and most women and older immunosuppressed persons are immune from having had chickenpox as a child. Transmission of zoster vaccine virus to household or other close contacts has not been reported.”_ [http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/genrec.pdf](http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/genrec.pdf) So it is possible for a live (attentuated) vaccine virus in some instances to be transmitted to a contact who is susceptible to infection, especially if that person is heavily immunosuppressed. In general however, it is much more dangerous for those immunosuppressed people to risk contracting wild-type infections from contacts, who should get vaccinated to prevent such an eventuality. ---
**Author:** ![clairobscur](https://avatars.discourse-cdn.com/v4/letter/c/839c29/32.png) [@clairobscur](https://boards.straightdope.com/u/clairobscur)\ **Post date:** [July 10, 2013, 3:03am UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/5 "2013-07-10T03:03:39Z")
> [@Reply](#): > > In childhood (and I don’t know how accurate this is), I was taught that vaccinations work by priming the immune system to recognize that specific microbe and successfully attack it before a full-blown infection occurs. Doesn’t that mean there’s a period of time when the microbe is in your body and your immune system is busy fighting it off? > ? I would assume that at this point the microbe isn’t present in large enough numbers for the person to be contagious. That’s just based on my understanding of what vaccination is. I’m completely unqualified to tell if it’s what happens. WAG, IOW. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [July 10, 2013, 7:48pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/6 "2013-07-10T19:48:24Z")
> [@Reply](#): > > In childhood (and I don’t know how accurate this is), I was taught that vaccinations work by priming the immune system to recognize that specific microbe and successfully attack it before a full-blown infection occurs. Doesn’t that mean there’s a period of time when the microbe is in your body and your immune system is busy fighting it off? > > And during that time, could you transmit it to non-vaccinated others if it’s still in your bloodstream? Again, the disclaimer - all of what I’m about to say is generally true, but there are exceptions, because it’s biology, and there are always exceptions. There are different kinds of vaccines. First are the so-called “dead” viruses. These are viruses that have been treated in some way to make them non-infectious. You inject them into the body so the body “learns” what the virus looks like and makes antibodies against them, but they cannot infect, reproduce, or spread to other people. There are also live virus vaccines, the most famous of which is probably the vaccinia virus, which is a close relative of smallpox, and very closely related to the virus that causes cowpox. Because of its similarity to smallpox, if you’re immune to vaccinia, you’re also immune to smallpox, and this is how vaccination all got started originally. You infect someone with vaccinia, which is pretty much harmless, and they’re then safe from the horrible smallpox virus. Vaccinia did have the ability to spread to other people. Other live virus vaccines take the original pathogenic virus and alter it in some way so that it’s no longer dangerous. These may or may not be infectious to other people, depending on how they were altered. ---
**Author:** ![Chief\_Pedant](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@Chief\_Pedant](https://boards.straightdope.com/u/Chief_Pedant)\ **Post date:** [July 10, 2013, 8:05pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/7 "2013-07-10T20:05:45Z")
Originally Posted by Reply Let’s say John is vaccinated against Disease XYZ. He catches it anyway but he’s fine because he’s vaccinated. But can John still pass XYZ onto somebody else? > [@Jackmannii](#): > > The bottom line is that this can occur if live virus vaccines are given, it’s unusual but not unheard of. I think the OP wants to know if a vaccinated patient will transmit an infection he acquires but which does not become symptomatic for him because he is vaccinated. This is different than transmitting the same live attenuated organism with which he is vaccinated, which is what your cite is referring to… There is such a thing as an asymptomatic carrier state for an assortment of organisms; I’ll try to comment more if I have time later. ---
**Author:** ![dstarfire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dstarfire/32/5762_2.png) [@dstarfire](https://boards.straightdope.com/u/dstarfire)\ **Post date:** [July 10, 2013, 10:38pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/8 "2013-07-10T22:38:33Z")
Let’s clarify the necessary facts for the question “is it possible for an person A (who’s vaccinated against infection xyz) to spread that infection to person B in the time period it takes for person A’s immune system to destroy the infection?” We need to know: [ol][li] How long can a virus, bacterium, or whatever survive in the body of a person who’s been vaccinated against that organism? (Assume it’s several organisms of the same species, since those bugs always travel in hordes)[/li][li] Is it possible for that organism to propogate or be ejected (intact) from the body in that period of time?[/li][li] What is the likelihood that one of those intact, ejected organisms will survive to infect a viable host?[/li][/ol] ---
**Author:** ![Chief\_Pedant](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@Chief\_Pedant](https://boards.straightdope.com/u/Chief_Pedant)\ **Post date:** [July 11, 2013, 11:20am UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/9 "2013-07-11T11:20:03Z")
> [@Reply](#): > > Let’s say John is vaccinated against Disease XYZ. He catches it anyway but he’s fine because he’s vaccinated. But can John still pass XYZ onto somebody else? Whether you are vaccinated or have a previous natural exposure to an infectious agent, you will have some residual personal immunity to that agent, assuming you are a normal host and cleared the infection normally. Should you be exposed to the germ again, you will not typically get re-infected personally (although realize that there are thousands of infections and medicine is full of subtleties and exceptions). This doesn’t mean that you can never be the vector through which that same disease is transmitted to another. One way would be if you are a very short-term resevoir. Let’s say someone with chicken pox slobbers you up and you then slobber up someone else. You could serve as the vector. But I think there are other, longer-term ways as well. For example, in many people the agent that causes a common and severe kind of meningitis (Neisseria Meningitidis) lives happily in their nasopharynx without causing them disease. This might be because they have better host defense, or it might be because the strain they carrier is missing some capsular component against which their prior innoculation (assuming they were vaccinated or had the disease in the past) formed antibodies. Without the capsular component, the germ lives placidly in their nostril but can kill the next guy over when they transmit it to someone else. Asymptomatic carrier states like that are one way someone who is personally immune can still be the one responsible for the next person over getting the disease even if the carrier has immunity from prior vaccination or actual disease. Your question can be more precisely answered with reference to a specific offending pathogen, I’d say, since the subtlety for each germ is quite profound. ---
**Author:** ![flatout](https://avatars.discourse-cdn.com/v4/letter/f/f04885/32.png) [@flatout](https://boards.straightdope.com/u/flatout)\ **Post date:** [July 11, 2013, 1:19pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/10 "2013-07-11T13:19:55Z")
> [@Reply](#): > > Let’s say John is vaccinated against Disease XYZ. He catches it anyway but he’s fine because he’s vaccinated. But can John still pass XYZ onto somebody else? This assumption that ‘he’s fine because he’s vaccinated’ is a long way wide of the mark. Lots of vaccinated people catch the disease against which they were vaccinated, a typical childhood vaccine may be 80-90-odd% effective. Even when it is, the disease may still be ‘caught’. As time goes by, efficacy wears off. I caught whooping cough as a child from a friend who had been vaccinated (I hadn’t) and he suffered more, for longer. My question is slightly different - if vaccination is as effective as the pharmaceutical industry would like us to believe, why are there the mass panics amongst those whose children are vaccinated, whenever there is an outbreak of virtually harmless measles? Surely they should be feeling smug, knowing their child has been injected? The other question is one of why bother in the first place, especially with diseases like measles which not long ago were regarded as harmless? The numbers of children killed and disabled by MMR is actually greater than the numbers killed/disabled after a measles infection. My answer? - perhaps it has something more to do with the billions earned by the industry. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [July 11, 2013, 2:07pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/11 "2013-07-11T14:07:50Z")
> [@flatout](#): > > The other question is one of why bother in the first place, especially with diseases like measles which not long ago were regarded as harmless? The numbers of children killed and disabled by MMR is actually greater than the numbers killed/disabled after a measles infection. My answer? - perhaps it has something more to do with the billions earned by the industry. Your assumptions are incorrect, so your conclusions are incorrect. ---
**Author:** ![Inner\_Stickler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inner_stickler/32/318_2.png) [@Inner\_Stickler](https://boards.straightdope.com/u/Inner_Stickler)\ **Post date:** [July 11, 2013, 2:27pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/12 "2013-07-11T14:27:17Z")
> [@flatout](#): > > My question is slightly different - if vaccination is as effective as the pharmaceutical industry would like us to believe, why are there the mass panics amongst those whose children are vaccinated, whenever there is an outbreak of virtually harmless measles? Surely they should be feeling smug, knowing their child has been injected? Because they have this thing called empathy where they worry for the unvaccinated children of idiots because it’s not fair for children to pay the price for their parents stupidity and because not everyone who understands the importance of vaccinations are able to be vaccinated. Infants, the immuno-suppressed and those with certain allergies are some of the groups that are put at risk when diseases like measles or pertussis spread. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [July 11, 2013, 4:05pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/13 "2013-07-11T16:05:25Z")
> [@flatout](#): > > The numbers of children killed and disabled by MMR is actually greater than the numbers killed/disabled after a measles infection This isn’t even close to being true. ---
**Author:** ![scienceguy151](https://avatars.discourse-cdn.com/v4/letter/s/7c8e57/32.png) [@scienceguy151](https://boards.straightdope.com/u/scienceguy151)\ **Post date:** [July 11, 2013, 5:16pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/14 "2013-07-11T17:16:18Z")
> [@flatout](#): > > The other question is one of why bother in the first place, especially with diseases like measles which not long ago were regarded as harmless? The numbers of children killed and disabled by MMR is actually greater than the numbers killed/disabled after a measles infection. My answer? - perhaps it has something more to do with the billions earned by the industry. That’s only because there are so few measles cases in America because most people are vaccinated. Just visit an orphanage in a country with poor public health programs and you’ll see that your assumption is wrong. Those kids are miserable when measles goes through. To answer the question, in theory you don’t retransmit. If you get measles virus on your hands and run to the nearest unvaccinated person then maybe. The issue of a live vaccine making someone else sick is another story. It’s supposed to grow normally and have a high viral titer for the strong immune response. If some of those viruses revert to wild type, those can make someone sick. See polio vaccine. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [July 11, 2013, 6:08pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/15 "2013-07-11T18:08:32Z")
The other issue is transmission method. In colds, and IIRC bubonic plague, for example, and TB - the infection results in the virus or germ being released into the air when a person breathes or sneezes. If you don’t get enough of an infection to create reservoirs of infection material in the lungs, nasal cavity, or whatever, you are not infectious. If you are immunized and show no symptoms after exposure then you don’t have bursting tubercules growing in the lungs and letting out bacteria, etc. ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [July 11, 2013, 6:57pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/16 "2013-07-11T18:57:02Z")
When the fuck was measles ever considered harmless? ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [July 11, 2013, 7:15pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/17 "2013-07-11T19:15:01Z")
As a further answer to the OP: influenza is an example of a disease where vaccination may not be totally protective, resulting in some vaccinated people coming down with flu of varying degrees of severity; even a mild flu infection could be transmitted to someone else. In general however, vaccination results in protection against even subclinical infection, so that there is no risk of transmission to others. ---
**Author:** ![Antigen](https://avatars.discourse-cdn.com/v4/letter/a/848f3c/32.png) [@Antigen](https://boards.straightdope.com/u/Antigen)\ **Post date:** [July 11, 2013, 7:36pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/18 "2013-07-11T19:36:58Z")
> [@purplehorseshoe](#): > > When the fuck was measles ever considered harmless? Only now, with a generation of morons who figure that since they’ve never seen anyone killed by measles, it can’t possibly be that big a deal. ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [July 11, 2013, 8:48pm UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/19 "2013-07-11T20:48:25Z")
> [@Chief\_Pedant](#): > > I think the OP wants to know if a vaccinated patient will transmit an infection he acquires but which does not become symptomatic for him because he is vaccinated. > > This is different than transmitting the same live attenuated organism with which he is vaccinated, which is what your cite is referring to… Right, exactly. > [@Chief\_Pedant](#): > > But I think there are other, longer-term ways as well. For example, in many people the agent that causes a common and severe kind of meningitis (Neisseria Meningitidis) lives happily in their nasopharynx without causing them disease. This might be because they have better host defense, or it might be because the strain they carrier is missing some capsular component against which their prior innoculation (assuming they were vaccinated or had the disease in the past) formed antibodies. Without the capsular component, the germ lives placidly in their nostril but can kill the next guy over when they transmit it to someone else. Thank you, that’s exactly what I was wondering. > [@md2000](#): > > If you don’t get enough of an infection to create reservoirs of infection material in the lungs, nasal cavity, or whatever, you are not infectious. If you are immunized and show no symptoms after exposure then you don’t have bursting tubercules growing in the lungs and letting out bacteria, etc. In the case of TB, how would an asymptomatic carrier know whether the bacteria is altogether gone (and unable to spread further) or just residing harmlessly in their lungs, infecting non-immune others all the time? ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [July 12, 2013, 3:33am UTC](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089/20 "2013-07-12T03:33:08Z")
> [@flatout](#): > > The numbers of children killed and disabled by MMR is actually greater than the numbers killed/disabled after a measles infection. From the CDC ([an excellent webpage](http://www.cdc.gov/vaccines/vac-gen/6mishome.htm) which discusses misconceptions about vaccines, and contrasts the frequency of serious complications from disease with the frequency of serious vaccine reactions): \*DISEASE ``` Measles Pneumonia: 6 in 100 Encephalitis: 1 in 1,000 Death: 2 in 1,000 Rubella Congenital Rubella Syndrome: 1 in 4 (if woman becomes infected early in pregnancy) ``` VACCINES ``` MMR Encephalitis or severe allergic reaction: 1 in 1,000,000* ``` As to the claim that vaccination is promoted so that “the industry” can earn “billions” - it apparently has not occurred to **flatout** that Big Pharma, physicians and hospitals can earn far more by allowing widespread outbreaks of vaccine-preventable diseases (consider the costs for example of antibiotics/antivirals, other medications and supplies, hospitalization including intensive care services, specialist fees and the like) than the income from vaccine sales. And if vaccines are so very lucrative, how is it that the number of companies manufacturing them has declined markedly in recent decades, to the point where shortages occur (as in a recent influenza season, where the U.S. had to import supplies on an emergency basis from abroad)? Instead of mindlessly chanting “follow the money”, antivaxers need to use their critical thinking skills (or whatever passes for them in such folk). [Next page](https://boards.straightdope.com/t/do-vaccines-prevent-retransmission/663089.md?page=2)