I have a friend who was invested in Moderna at the right time, though she sold before it was really the right time, if you get the drift. Still made out decently well.
One influential person? The first person who comes to mind, who might listen if he knew his visitor was from the future, is Herman Cain. Basically telling him to take it seriously, or he would live to regret not doing so, and to encourage others to as well.
Would it change the course of events? Unlikely. But he was at least marginally influential, and old enough to possibly take a different course with some warning of what the future might hold.
As it was, I did write to some of my representatives in 2020, and saw at least one of them implement one of my suggestions, although possibly coincidentally.
The bigger question is, who could have the most impact who misunderestimated the impact in 2020, and might have listened? And what would the greatest impact have been? I can think of a few candidates. Vladimir Putin, or an appropriate deputy, on being more cautious about Sputnik rollout, so the trust in it would be higher and correspondingly its uptake. Winning the rollout battle was not worth it in the end. Someone in the Indian government, encouraging more local vaccine rollout (and highly localized, perhaps?) to try to retroactively prevent Delta? February 2020 means it's already too late to warn someone in China that they should sound the alarm bells sooner; it's in Iran, Italy, the U.S., etc. The Brazilian government is practicing ignorance, and aside from the travel ban from China and the vaccine funding, the U.S. government largely is as well, and the people at the top wouldn't listen anyway. BoJo would start taking it seriously in April and would have limited potential impact on the world at any rate. So in the end, I guess I'd lean towards either someone high up in Russia to try to improve Sputnik outcomes, or someone in India to try to prevent Delta.
Or maybe the CEO of Pfizer, Bourla, to try to persuade him to advocate for universal production of vaccines. Pfizer would already become fabulously wealthy regardless; if they had advocated building factories worldwide earlier, abandoning their patents with knowledge that their investments would be rewarded tenfold or more regardless, perhaps vaccine rollout would have progressed more quickly in 2021, potentially forstalling omicron and blunting the impact of delta. Would he have been persuadable that the net positive impact to society would be worth reducing the profit potential, while still leaving it quite large? Perhaps not, but it seems like a third candidate for someone who may potentially have been able to have a significant impact.