The mRNA vaccines are effective against E484K variants like Gamma. While neutralizing antibody levels are multiple-fold lower than against original Wuhan strain, real-world protection appears strong (very strong for severe disease).
Thus the "strategy" of relying on immunity through previous Covid infection is bad, and the doctor who advised it is giving bad advice. Right now, if group911's friend gets exposed to SARS2 virus - as he surely will, since masking/distancing is rapidly ending - it is most likely to be Delta, but there is a 10% chance it will be to P1/Brazil/Gamma whose ability to reinfect and hospitalize him is pretty clear. Not to say that he is actually immune to reinfection with Delta, the data just isn't available yet. For him to refuse vaccination is simply stupid, on his doctor's part and his own part.
https://covid.cdc.gov/covid-data-tracker/#variant-proportions