Mammal milk contains lactoferrin, a very powerful anti-viral/bacterial/fungal molecule that helps fighting invaders in your gut. Lactose-free milk would still work to avoid age-related digestion issues. By skipping it you are likely going to develop gut issues in a few years/decades. See the clinical section here: https://en.wikipedia.org/wiki/Lactoferrin
"Lactoferrin in sufficient strength acts on a wide range of human and animal viruses based on DNA and RNA genomes,[46] including the herpes simplex virus 1 and 2,[47][48][49] cytomegalovirus,[50] HIV,[48][51] hepatitis C virus,[52][53] hantaviruses, rotaviruses, poliovirus type 1,[54] human respiratory syncytial virus, murine leukemia viruses[43] and Mayaro virus.[55] Activity against COVID-19 has been speculated but not proven"
"Lactoferrin in sufficient strength acts on a wide range of human and animal viruses based on DNA and RNA genomes,[46] including the herpes simplex virus 1 and 2,[47][48][49] cytomegalovirus,[50] HIV,[48][51] hepatitis C virus,[52][53] hantaviruses, rotaviruses, poliovirus type 1,[54] human respiratory syncytial virus, murine leukemia viruses[43] and Mayaro virus.[55] Activity against COVID-19 has been speculated but not proven"