There are parents and doctors that agree to spread out their kids' shots. Supposedly it's easier on the baby (some babies experience fever or other ill reactions to vaccination).

But I had a thought that maybe the fever after a certain shot might be the same regardless if it's taken together with another shot or not. Or maybe the ill effect even increases as the break between shots gets reduced and there is less time for body to recover for the next shots?

Is there any evidence that taking shots one by one reduces the ill effects?


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There is evidence that delaying or refusing immunization puts children at risk of disease here and here. There is also evidence that delaying or spreading out MMR or MMRV in particular puts children at greater risk of reactions (febrile seizures), rather then reducing the risk. I'm not aware of any study demonstrating the opposite.

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    Correct. The only one I am sure about is a minuscule increase in risk of febrile seizure if you administer the combined single shot with both MMR+Varicella instead of two separate shots of MMR and Varicella (even if given in the same leg at the same time!) but that's in a very narrow age group. MOST spacing out of vaccines is done simply for patient/parent preference, so as not to have to endure so many pokes in one visit. I will find the reference for that... I have this conversation often. Evidence points to (and I'm all for) getting then done as soon as eligible & build protection ASAP.
    – DoctorWhom
    Nov 13, 2018 at 7:11
  • @DoctorWhom re: MMRV, if I recall, the evidence was that the increased risk of febrile seizures was the relative risk of the combination vaccine vs. MMR and Varicella in two separate injections, and is more of any issue with that vaccine than with the schedule.
    – De Novo
    Nov 13, 2018 at 15:46
  • @Narusan and DeNovo - Perhaps I wasn't clear enough - that was intended to further emphasize that the schedule is usually followed at earliest eligible date, when not it's just for parent preference not because of evidence, and there is next to zero reason for spacing out vaccines. I am 110% for getting vaccinated for everything possible. Should I delete my comment if it is distracting?
    – DoctorWhom
    Nov 13, 2018 at 16:27
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    @Narusan yes, it's been a while since my peds rotation, but young kids are most definitely afraid of going to the doctor because of shots. I remember being afraid myself, and that was quite some time ago. I only meant to say we have to be careful when we talk about these things. You don't want someone saying: "I'm not going to vaccinate my kids because Narusan said vaccines cause a life long fear of doctors".
    – De Novo
    Nov 13, 2018 at 16:33
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    I honestly think that lifelong traumatizing is a RARE phenomenon. Kids who are afraid of the doctor seem to grow out of it after age 5 or so.
    – DoctorWhom
    Nov 13, 2018 at 17:14

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