Peg,
That is a very good question. Agree, this is not a place to debate vaccines. Even more, we do live in a free society and it is up to parents to do their own research and to make their own conclusions.
So with your permission I would break it into two parts.

1. The concept of vaccination delay in general. This is a very popular concept and here is my take on it. In 1970s, aft a couple of kids did die in Japan following DPT vaccination, DPT vaccination was stopped. When even more kids did die because of whooping cough disease (history is silent re: how sick did survive, but we do know from the recent epidemic - that was not pretty), new acellular vaccine, DTaP, was introduced. In Great Britain DTP vaccine was blamed in cases of the infantile spasms, debilitating seizure disorder of infancy, that usually affects infants between 4 and 6 months of age. DPT vaccination was officially delayed till 12 no or so. The result was devastating - no effect on infantile spasms, but too many deaths from whooping cough.

Delayed and/or "spaced" vaccinations are also known to lead to incomplete vaccination courses and and as such - to decreased protection.
Even more, some vaccinations can not be started or given after certain age and therefore by delaying vaccinations parents can risk reducing the immune protection of their child 

These age specific pediatric vaccines are: rotavirus vaccine ( vaccination should be initiated between 6 and 14 weeks of life and all doses should be administered before 8 months of age), Hib vaccine ( ( if vaccination is initiated before 10 months the kid will get 3 doses before the first birthday and one dose between 12 and 15 months; initiation after 12 months but before 15 months will reduce the course to 2 doses, waiting till 15 months will allow to only 1 dose and no doses are given after the 5th birthday; pneumococcal vaccine has similar age limitations with one exception - 2 doses can be given if vaccination is started before the age of 2 years)

Understanding that HiB and pneumococcal infections are mostly affecting kids between 2 months and 5years, not starting these vaccinations at 6-8weeks can have a devastating effect on the kid's health and even life.

While some parents will voice the desire to provide "natural" immunity to infectious diseases, one should remember that (a) in order achieve said natural immunity one first have to survive the infection and (b) that natural infection should preferably be more effective then vaccine-induced immune response. For example in order to get natural immunity against tetanus one should be in the lucky 40% of those who will survive in intensive care unit (intubation and so on) and even then the "naturally" obtained immunity will be inferior to the vaccine-induced protection.
Vaccines that are giving better protection then natural disease: tetanus, HiB and HPV. Rotavirus is it seems to me is the other one on that list but I don't have data on it handy.

2. The effect of breastfeeding on vaccinations. There is only one vaccine that can be potentially affected by breastfeeding and that is the rotavirus vaccine. The thought is that the effectiveness of this live oral vaccine can be reduced by antibodies in the breast milk and therefore it is advised to delay breastfeeding immediately after the rotavirus vaccination, meaning - do not breastfeed immediately after the immunizations, feed the kid just before the visit and then he/she can safely wait till the next feeding. That's it. Simple and easy. There is nothing in recommendations about weaning. Unfortunately that simple and reasonable recommendation was distorted in multiple flaming blogs and posts over the internet, but that is not the first and, unfortunately, not the last case of such flaming.

So yo did absolutely right by asking this question.
Hope that information helps.

Alla Gordina, MD, IBCLC, FAAP
General Pediatrics
Adoption Medicine
Breastfeeding Medicine

Global Pediatrics and Family Medicine
Breastfeeding Medicine Education Initiative

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Peg Merrill <[log in to unmask]> wrote:

>I seem to remember seeing a study several years back that immunizations
>weren't as effective if a child was still being breastfed and suggesting
>that it would be better to wait until after baby was weaned to start
>vaccines.  Does anyone else remember this, or is it just a figment of my
>aging brain?  Don't want to debate vaccines, just want to give my son some
>evidence to suggest that delayed vaccines have merrit.
>Peg Meiirll, IBCLC
>
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