I have since moved on from Inflectra but was on a four-week interval of Inflectra for a couple years. I had the same question about
risk of infection. This may be different from person to person but my doctor informed me that there is NOT an increased risk. It's likely you're going up in frequency because your levels are not high enough/ you're not responding as well, which indicates there is not enough medicine in your system to be considered therapeutic. This means your body is metabolizing the medicine quicker at eight-month intervals (than it would at four-month) so you have to refill earlier, kind of like a tank of gas. So technically, there is not MORE medicine in your system because your body is cycling it out, so the risk of infection would remain the same. This is from what my doc told me just FYI so it's simply my experience. Just email your GI and ask this question I'm sure they get it a lot