Final answer:
The correct action a nurse should take for a pregnant client at 22 weeks gestation who is HIV positive is to initiate antiretroviral therapy, as it significantly reduces mother-to-child transmission rates.
Step-by-step explanation:
A nurse caring for a client who is at 22 weeks gestation and is HIV positive should take the following action: initiate antiretroviral therapy. This approach has been proven to be effective in preventing mother-to-child transmission of HIV. Administering antiretroviral medications to the mother during pregnancy and to the infant after birth can reduce the transmission rates to about 1 percent. It is also important to note that live attenuated vaccines are not recommended for HIV-positive individuals because their immune system is compromised. Instead, preventive measures such as antiretroviral therapy are key for reducing the risk of further immune system damage and managing the condition effectively.