Infection generates natural immunity

Which seems good and long lasting and cheap, lots of evidence below. (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. 95% of participants tested retained immune memory at about 6 months after having COVID-19 More than 90% of participants had CD4 T-cell memory at 1 month, and 6–8 months after having COVID-19 Wang et al (2021) Science, Ultrapotent antibodies against diverse and highly transmissible SARS-CoV-2 variants Previous SARS-CoV-2 infection, with an ancestral variant produce antibodies that cross-neutralise emerging variants of concern with high potency Epidemiological studies Hansen et al (2021) Lancet, Assessment of protection against reinfection with SARS-CoV-2 among 4 million PCR-tested individuals in Denmark in 2020: