Q. Is there any chance of developing an HIV infection after starting post-exposure prophylaxis within 24 hours?

Answered by
Dr. Basti Bharatesh Devendra
and medically reviewed by iCliniq medical review team.
This is a premium question & answer published on Nov 09, 2022

Hello doctor,

I had unprotected vaginal sex with a masseuse and started post-exposure prophylaxis with Viropil within 24 hours. On the 19th day of the post-exposure prophylaxis, I had vaginal sex with my girlfriend. The next day, I had a fourth-generation HIV test, and the result was negative. My HIV counselor said that the risk of HIV was very low as I had post-exposure prophylaxis within 24 hours and completed almost three weeks of post-exposure prophylaxis. What is your suggestion about this?

1. Is there any chance of transmission of HIV from me to my girlfriend?

2. How accurate is a fourth-generation HIV test?

3. Do my girlfriend need to have post-exposure prophylaxis?

Kindly help.

Thank you.



Welcome to

I read your query and understand your concern.

The chances of transmission of HIV (human immunodeficiency virus) by a single unprotected intercourse is low. Post-exposure prophylaxis (PEP) initiated within 24 hours is a very good sign though not 100 percent protective. If the person is HIV-negative, then you need not worry. Fourth-generation HIV test is considered almost conclusive after one month of exposure and not on the 19th day. Therefore, the chances of HIV tests coming positive later are low. The risk of HIV transmission is very low for your girlfriend also. You can discuss with your doctor for further risk assessment and the need for PEP. If required, PEP must be initiated as early as possible, not after 72 hours of exposure.

Thank you.

Hello doctor,

Thank you for your response.

I understand that the fourth-generation HIV test is conclusive after 28 days, and I took the test on the 20th day of exposure. Is the test done on the 20th day of exposure not accurate?

Thank you.



Welcome back to

The fourth generation test is considered almost conclusive after one month of exposure. Still, many do not rely on it entirely. This is because the chances of HIV tests coming positive later are almost nil. I suggest you do an HIV antibodies test after three months of exposure for conclusive results.

Thank you.

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