You're comparing two different types of situation: the first is a direct casual relationship: if you get infected with the COVID-19 virus, you are less likely to infect others and are an order of magnitude less likely to die from it if you've been vaccinated — and that's a non-hypothetical situation with how widespread it is and the strain this has placed on the healthcare system, impacting patients with completely unrelated needs.

In contrast, the link between GMOs and food insecurity is nowhere near that simple. If you are starving because you are a member of an ethnic group which is not in power, GMOs won't do a thing. If you are starving because you don't own your farmland and the owner charges too much in rent, GMOs won't change that dynamic. If you are starving because you lack adequate water or have contaminated farmland, GMOs may or may not help enough to make a difference. If you are starving because insects or fungus destroy your crops, GMOs might help if you can afford the seeds but not if, say, they help by letting the crops survive if you spread pesticides which you can't afford. If you are starving because your lack of access to birth control means that you (as was common throughout human history) have more children than your farmland can feed, GMOs probably won't help enough to change your life. If you are starving because other economic conditions force you to sell too much of your crop to pay for other things like shelter, clothing, medicine, etc. GMOs won't really help, either. If you have any of these problems and the company which made the GMOs won't sell you seeds at an affordable price, well, guess what?

That's not saying that GMOs don't have a useful place — as you might note, I described them as necessary for the impacts of climate change on agriculture — but unlike COVID there isn't a single problem and it's not something which can be fixed with a cheap, infrequent action. The problems GMOs help with are only part of a complex set of overlapping problems and they don't solve anything as much as they help manage it — American farmers jumped on Roundup-resistant crops for obvious reasons but it wasn't a game changer for them because the benefits are partially canceled by the ongoing cost of buying seed and pesticides.