MDPI's business practices have attracted controversy, with critics suggesting it sacrifices editorial and academic rigor in favor of operational speed and business interests.

MDPI is a well-established publisher of open-access journals, with a good reputation in the scientific community. While concerns about predatory publishing practices are valid and should be taken seriously, it is important to approach such claims with caution and to evaluate the evidence carefully.

Vaccines (ISSN 2076-393X) is an international, peer-reviewed open access journal focused on laboratory and clinical vaccine research, utilization and immunization. Vaccines publishes high quality reviews, regular research papers, communications and case reports.

Yes, Frontiers is a predatory journal. Regardless, they are a huge producer of the scientific articles that enter the literature: 3rd most cited and 6th largest publisher! That's a lot of papers that go through the same "peer review" process that let this through.