Yes, Erin. I might just broaden your question a little bit, and I'll get to it. I think it's really important. I know innovation and these blockbuster products, specifically Zenrelia and Credelio are important to all of us. So let me just add a little framing to the comments I made when I opened the call here.
First, we are very pleased with the progress we've made in these key assets. Since February, actually, a lot of progress has happened, and that's driven our increased certainty as we move closer to the end of this approval process.
Yes, the dialogue with the FDA has been rolling and iterative. We've been in a productive engagement with them, Erin. It's been fair, constructive, frequent. And really, over the last several months, we've been responding to the questions from the agency, which is very common, I believe the Animal Drug User Fee Act or ADUFA is working specific on these assets. It's been constructive.
So what's changed and what has not changed since February? What has changed is, many sections and subsections of these submissions have been approved. Both products have progressed. Simply though, the back-and-forth interactions have taken slightly more time than when we estimated this path to first half approval. Thus, we're not moving the final 60-day administrative review into the third quarter. And I think importantly, we have increased certainty in the timing from all of this interaction that you mentioned.
I think it's also important to say what hasn't changed? What hasn't changed is we continue to expect the products to be differentiated versus the current offering. We still expect all technical sections, including the label, to be approved in the first half or by the end of June. And we expect that revenue contribution is still expected in the second half for these 2 products as well as Bovaer.
And again, importantly, we believe the FDA has what they need for the approvals, and the launch planning to your question on that, and the marketing is well underway. The U.S. Pet Health is well positioned right where we believe it needs to be relative to the launches. We're as competitive as we've ever been. A good, nice lead indicators, engagement scores in U.S. Pet Health. They're as high as they've probably been in years and the highest, I think, in the global company.
So that's a nice lead indicator that our preparedness is ready. We will launch as soon as possible as we've noted. We expect that right now to be Q3 for Zenrelia, Q4 for Credelio Quattro.