> We hypothesise that the SARS‐CoV‐2 infection triggered an anti‐tumour immune response
A completely different hypothesis: what if the tumor was sustained by the EBV infection, and SARS-CoV-2 displaced or outcompeted it? There are signs that viruses can compete and suppress each other, e.g. influenza rates have apparently dropped dramatically during the SARS-2 pandemic.
"Triggering an immune response" is probably the mechanism (perhaps tautologically: everything viruses do is done by commandeering the host's cells, and having them kill another virus would be classified as "immune response"), the difference is that viruses may have evolved ways to actively stimulate immunity against rival viruses.
There's no way to say that conclusively. Influenza also spreads via aerosols, and the size of the virion is in the same range as that of the coronavirus. It's unclear why the same physical measures, applied with the same degree of compliance, should fail to stop one but nearly completely stop the other.
A completely different hypothesis: what if the tumor was sustained by the EBV infection, and SARS-CoV-2 displaced or outcompeted it? There are signs that viruses can compete and suppress each other, e.g. influenza rates have apparently dropped dramatically during the SARS-2 pandemic.
"Triggering an immune response" is probably the mechanism (perhaps tautologically: everything viruses do is done by commandeering the host's cells, and having them kill another virus would be classified as "immune response"), the difference is that viruses may have evolved ways to actively stimulate immunity against rival viruses.