Answer: They can’t.
“But…but, you see, we take a piece of RNA, and we inject it into the person, and the RNA forces the cells to manufacture a protein that’s very similar to a protein in SARS-CoV-2…and then the immune system swings into gear and produces antibodies to THAT protein, and THEN the person has achieved immunity from the virus…”
Sorry, no dice.
As I’ve been demonstrating for months now, there is no proof that SARS-CoV-2 exists  . Therefore, “the piece of RNA” that’s injected can’t be assumed to be related to “the virus.”
Therefore, the protein which the cells produce in the body is merely CLAIMED to be similar to a protein in the unproven “SARS-CoV-2.”
There is no KNOWLEDGE here.
That piece of RNA which is injected into the body—why should we assume it has anything to do with a virus called SARS-CoV-2, when no one has an isolated specimen of this “SARS-CoV-2?”
We shouldn’t assume…
David Rasnick , PhD chemist, with a long history working in the pharmaceutical industry (Abbott, Prototek, Arris), broke away from official science and served as the president of Rethinking AIDS: the group for the scientific reappraisal of the HIV hypothesis. He was a member of the Presidential AIDS Advisory Panel of South Africa.
Here is a recent explosive statement Rasnick made  about SARS-CoV-2 and HIV. Digesting it brings about a breakthrough revelation:
“Viruses are unstable, RNA [e.g, SARS-Cov-2] viruses especially. They are so unstable, there is no such thing as an un-mutated RNA virus. They are like snow flakes, no two are identical.”
“HIV is an RNA virus with 9,800 nucleotides. You can download the HIV Sequence Compendium here:” 
“In the Preface it says:”
“’The number of [genetic] sequences in the HIV database is still increasing. In total, at the end of 2017, there were 812,586 sequences in the HIV Sequence Database, an increase of 8.5% since the previous year.”
“None of the sequences of the world destroying [sarcasm], computer generated coronavirus with its 30,000 or so nucleotides, are identical.”
“The virus maniacs use computers to compare the menagerie of sequences to come up with ‘A Consensus Sequence’ for HIV, Coronavirus, and all the rest. The consensus sequence exists in two places: in computers and in strings of RNA synthesized in the lab.”
“Even consensus sequences are not stable. Different groups, using a variety of computer algorithms will invariably come up with different ‘consensus sequences’.”
The implications of Rasnick’s statement are enormous…
Quote from the following article:
You can view the work of Christine Massey at her site, fluoridefreepeel.ca (also, twitter: ). She deserves the thanks of every thinking person.
Quoting Massey : “I (CM), along with some anonymous helpers, have submitted Freedom of Information requests to various Canadian institutions seeking records that describe the isolation of ‘SARS-COV-2’ (the alleged ‘COVID-19 virus’) from an unadulterated sample taken from a diseased patient.
“My requests were intentionally worded to weed out the fraudulent, illogical and unscientific claims of having ‘isolated SARS-COV-2’, of which there are many…”
“My requests were not limited to records of isolation performed by the respective institution, and not limited to records authored by the respective institution, rather they were open to records of isolation performed by anyone, anywhere on the planet.”
“Colleagues in numerous other countries have obtained responses to the same and similar information requests from dozens of additional institutions.”
“As of January 22, 2021 46 institutions and offices have responded to said requests. Every institution has failed to provide, or cite, even 1 record describing the actual isolation of any ‘SARS-COV-2’ from a patient sample by anyone, anywhere on the planet, ever.”
Here is a typical response to a Massey request, from the Ontario Ministry of Health. The response arrived after four months: “This is to inform you that no responsive records were located. A reasonable search of the ministry was conducted, and no responsive records were found. Dr. David C. Williams, Chief Medical Officer of Health, is responsible for this decision.”
NO records indicating SARS-CoV-2 has been isolated. “Isolated” means “separated from other material.” It means “we actually found the virus and could identify it.”
ACTUAL ISOLATION MEANS THE VIRUS EXISTS. INABILITY TO ISOLATE IT MEANS THERE IS NO PROOF THE VIRUS EXISTS… (emphasis mine)