Which seems good and long lasting and cheap, lots of evidence below. https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00676-9/fulltext Biological studies Dan et al (2021) Science, Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection. https://www.science.org/doi/abs/10.1126/science.abf4063 95% of participants tested retained immune memory…