A director of the Rexx Pharmaceutical Company argued that the development costs for new vaccines that the health department has requested should be subsidized by the government, since the marketing of vaccines promised to be less profitable than the marketing of any other pharmaceutical product.
Conclusion
The development costs for new vaccines the health department requested should be subsidized by the government.
Intermediate Conclusion
The marketing of vaccines will be less profitable than the marketing of any other drug.
Evidence
Sales of vaccines are likely to be lower since each vaccine is only given once, whereas other drugs are administered many times (so that the drug manufacturer has more opportunities to make back their R&D costs)
Evaluate
The question stem isn't a typical Weaken stem; it's asking us to Weaken the intermediate conclusion. We can still use our normal Weaken mindset:
Given That vaccines are only administered once, whereas other drugs are administered multiple times
How Can We Argue That the marketing of the vaccine could be as profitable as that of other drugs?
Maybe this is an atypical vaccine (like the coronavirus or flu vaccine, potentially) where people will need to get it every year, or maybe even more frequently than that.
Maybe this vaccine will cost a lot more money for patients / insurance companies than do most vaccines (so that even though the drug company only gets one blip of revenue, it's a big blip!)
Maybe this vaccine is so desperately needed that almost everyone is going to buy it, whereas these other drugs that get administered multiple times are only sought after by a small audience.
A million one-time purchases might be more revenue than 10,000 recurring purchases.
Goal
Because the author's argument is comparative, in order to break out of her logic, we probably need to highlight a meaningful difference between this vaccine and other vaccines, or between this one-time vaccine and other drugs, which are given multiple times.