Science Questions

Can vaccines be given together?

Sun, 1st Nov 2009

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Steve Junk asked:

Can vaccines can be given together? I know someone that just received four vaccines at once. Can they wear out the immune system and not produce as good a response?


Chris - The answer is both yes and no actually.  When you give vaccines to people, what you're aiming to do is get the immune system to respond so that it can recognize that pathogen in the future and protect you either with antibodies or cells that kill viruses in cells.  Now, one way of vaccinating people is what’s called Live Attenuated Vaccine.  This is where you grow viruses in culture for many generations and through the effects of mutation, they lose the ability to make you ill, but they nonetheless remain infectious.  So, with the MMR, Measles, Mumps and Rubella, for example, you put the virus into the person.  It doesn’t cause severe disease, but what it does do is to display to the immune system the entire repertoire of viral genes, viral proteins.  And what that does is it makes a very broad immune response, involving making both antibodies and cells that can attack virally infected cells.  That way, your body is very powerfully primed to recognize and prevent you from getting that virus in the future.  The problem is that when you go into that state of infection, what it does is to release large amounts of a signalling hormone called interferon, Alpha interferon in fact.  And what that does is put all the cells in the body into this antiviral state where the cells are undergoing surveillance.  They increase the surface markers, they displace the immune system so that they're more likely to get killed if they’ve got a virus in them, they degrade genetic material that they think might be viral, and they become much harder to infect for viruses.  Now that means if you've had one virus, that’s attenuated vaccine, about a week or two before, your body makes load of this interferon.  If you then come along and then try and infect yourself with another attenuated virus, for instance another vaccine, it won't work very well because it doesn’t get into the cells, and the body kills it really quick before it has a chance to prime your immune system.  So live vaccines, if you don't have them at the same time, but you have them all together is a bad thing to do.  Having them all together is fine because the immune system works by discriminating very powerfully between different epitopes that different viruses display anyway.  So that’s not a problem.  For the present situation we’re in now though, people are asking me, “What about flu vaccines?”  Because lots of people had a seasonal flu vaccine but then they're also saying, “Well now, we need to have a swine flu vaccine.  Will the fact that I had the seasonal vaccine about two weeks ago make a difference for me having the swine flu vaccine now?”  And the answer is not in that circumstance.  No, because the flu vaccine is a killed vaccine.  You're just putting in bits of dead virus, shrapnel if you like which the immune system then learns to recognize.  This doesn’t trigger the same interferon response so it doesn’t make you feel ghastly in the same way.  It doesn’t actually prevent you getting infected with other viruses in the same way.

Dave -   Is this interferon response, the reason why I still feel really quite shattered now, two weeks after I had the flu?

Chris -   Yeah and the reason that flu makes you feel so rotten, despite the fact that the virus is only confined to your respiratory tract, nose and throat, and sometimes lungs if you get a very severe infection, you probably had symptoms that were nonetheless across your whole body.  Muscle aches and pains, tiredness, very bad headache, temperatures, just feeling ghastly.  That’s because  of these hormones, the interferons that the body produces in response to the infection which then turn all of your cells into this very antiviral prime state.  So, exactly right, yeah and that’s why after some vaccines that do provoke lots of interferons to be released, you have a day of feeling a bit rotten.  It’s not because you’re infected, although you might be.  It’s actually the interferons – it’s your body’s own hormones that are making you feel like that.


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Steve Junk asked the Naked Scientists: Hi Dr. Chris, I listen to your podcast on my long commute.  My question is, How many vaccines may be given to a patient at one time? Are there certain combinations that may be particularly problematic? Someone I know just received four vaccine injections in one office visit.  All is well, but it "begs the question".  Can the immune system become "preoccupied" or otherwise degraded as a result of work it is doing "computing" or manufacturing an antibody for one pathogen, such that countermeasures against a second, third or fourth pathogen may produce ineffective antibodies or even decremental effects?  Does the name cold sores imply this effect?  Having the HLA-b27 gene, and having gone through a bout with reactive arthritis triggered by C. jejuni, I know our immune system can be a powerful adversary as well as an essential guardian.  Can the immune system be overwhelmed by the diversity and numbers of pathogens - has a limit been identified? P.S. What's Dr. Karl really like? Steve Irvine California What do you think? Steve Junk , Fri, 2nd Oct 2009

Hi Steve

The evidence is that the body can respond to more than one vaccine at once but they should be given simultaneously and not when a person is already suffering from another infection.

This is because when the immune system responds to a foreign agent, including an infection or a vaccine, it produces signalling hormones called interferons. This place cells all around the body into an antiviral state whereby they degrade genetic signals that appear to be foreign and also upregulate cell surface markers that indicate viral infection.

Therefore, if you administer a new vaccine once cells have already been primed in this way, the vaccine - particularly if it's a live vaccine like MMR, chickenpox, yellow fever - might struggle to gain a toe-hold and therefore the amount of immunity it triggers will be reduced.


P.S. Dr Karl is a great guy, incredibly clever and an inspiration to us all. I've never met anyone who can write so well and so prolifically - he's published over 27 books now - and I strive to be as good as he is!

C chris, Sat, 3rd Oct 2009

The body can respond to several vaccines at once; of course it can. The body doesn't know that the vaccine is "medical" it just treats it as a potential threat.
If it couldn't cope with a handfull of vaccines at once how could it cope with thousands of different bacteria at once? Since it does that every day... Bored chemist, Sat, 3rd Oct 2009

One thing I should probably add is that the interferon-induced state resulting from exposure to a viral infection or a live vaccine will have an impact on the administration of another live vaccine while this is taking place.

But exposure to killed vaccines - which are effectively just bits of protein - are less likely to be compromised in this way and may safely be given in a staggered fashion.

This very question has surfaced a bit lately with people who have recently received a seasonal flu vaccination and are now being offered a swine flu vaccination a week or two later. There's no problem with this pattern of administration.

Chris chris, Thu, 5th Nov 2009

Hi! I'm really sorry but I don't understand this: So live vaccines, if you don't have them at the same time, but you have them all together IS A BAD THING to do. Having them all together IS FINE because the immune system works by discriminating very powerfully between different epitopes that different viruses display anyway. English is not my first language, for me it looks as in the first sentence the same thing is bad, and in the 2nd is good... And the difference between 'having them all together' and 'having them at the same time' would be the first one, 1 single injection with all the vaccinations and the 2nd one different needels being put in difference of minutes? I'm about to travel so SEA and seems that everybody gets 4 different vaccinations (4 needles) the same day, but I;m not sure how good that is.. If you could answer my questions I would really appreciate it! Thanks a lot! Gabi Fanelli, Sun, 3rd Apr 2016

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