Op I’m a bit confused about what your child actually received. Assuming this was recently, their first vaccine set according to the schedule would be three injections for the 6-in-1, PCV, and MenB jags, plus maybe oral rotavirus. How many injections did your baby receive? I agree with others that you should proceed with caution in case your baby has a particular sensitivity.
I think people talk at cross purposes a lot when discussing separating out vaccines, with some talking about splitting the components of multivalent vaccines and others (most I think) talking about doing the injections one at a time. Considering a single multivalent jag like the 6-in-1 I have no issues with multiple antigens (the bits of individual organisms), as these are not likely to overstimulate the immune system. I wish they could put all the antigens for all the diseases in the schedule in one jag to get it over with, provided that was still one dose of adjuvant. The adjuvant is the ingredient that stimulates the immune system, usually aluminium, and each jag has it in because it wouldn’t work otherwise. This is why spreading out the injections generally leads to less severe side effects. There are maximum advisable limits for aluminium set out by the FDA, as this is a toxin, and you’ll see from another thread on spreading out vaccines that the current U.K. schedule actually exceeds these levels. In that sense, the multiple injections could be viewed as too much for their bodies, but this is an argument for spacing injections (and thus adjuvant doses) rather than avoiding multivalent vaccines. Note, I am definitely not advocating avoiding vaccines altogether as the reduction in severe disease is universally accepted by the scientific community.
The 5 in 1 and the 6 in 1 have been around for quite some time, so it’s difficult to say that the current cohort were a test population. The only jag in the first set that could fit this description is the MenB, as this is new and under active surveillance, and it’s safety and effectiveness are being actively studied (clinical trials are usually relatively small in scope and so post marketing surveillance is critical to get a full picture). This data was recently pulled together for Lancet Infectious Diseases (link below) and showed a serious adverse reaction rate of 5.4/1000 (almost 5 times higher than other vaccines in the schedule) and good immunity (defined as >75%) to only 2/4 antigens 6 months after the booster dose (so poor effectiveness compared to other vaccines).
www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(18)30048-3.pdf