The phrase "are now immune" is correct and usable in written English.
It can be used to indicate that someone or something has developed immunity at the present time, often in the context of health or protection against a disease or threat.
Example: "After receiving the vaccine, the participants are now immune to the virus."
Alternatives: "have now developed immunity" or "are currently protected".
Let (S_{h}(t)), (I_{h}(t)), (R_{h}(t)) and (V_{h}(t)) denote the numbers of susceptible (individuals who can contract the disease), infectious (individuals who are capable of transmitting the disease), resistant (individuals who have recovered and acquired immunity) and vaccinated (individuals who were vaccinated and are now immune) individuals at time t, respectively.
That is unknowable, most experts said, because no studies show how many people are now immune through previous infection.
Maybe, in fact, we are now immune to the visual shock of contemporary art on this most rigorously 19th century of squares.
The young illegal immigrants who are now immune to deportation are a very particular group: people who came here before they were sixteen, who are under thirty, and have lived in the States for at least five continuous years.
Six full years after the poll tax's demise, an estimated 4,000,000 people who declined to pay as much as £5 billion of the controversial levy are now immune from prosecution.
These people are now immune from the influence of Alice's new hat, though they may still be persuaded by someone they appreciate more.
I assume I'm now immune to all of the viruses that struck me then.
Some parents may be assuming that if their children were hit by swine flu in the spring, they're now immune -- a view shared by most flu experts.
Examples from China have shown that the global methodologies of benchmarking are now finding traction, demonstrating that no area is now immune to the global movement of performance evaluation.
The party's rules were very different then, however: Mrs. Thatcher was headed for a second, more bruising round of balloting, while Mrs. May is now immune from further Conservative Party votes for a year.
