On 7/12/20 I had sex for the last time with my ex-girlfriend as I was diagnosed with ureaplasma (STI) on 7/15/20. First treatment failed so I was placed on Doxycycline 3 weeks later.

3 days on Doxycycline, I developed a very strange flu like illness and weirdly enough a burning tongue with a white coating. I went to my doctor and had a laboratory 4^th generation HIV test done on 8/12/20 which was negative at 30 days from the last time I had sex.

I returned 3 weeks later on 8/31/20 (50 days from sex) for my follow-up test after the 45-day window period and to test my tongue for thrush as nystatin had not cleared the white coating. This test was negative and I was advised that I was HIV negative as I had tested outside the window period. Thrush was also negative.

I unfortunately never got tested for Covid, but suspect that was the cause of my strange flu like illness as I have never had a reaction to doxycycline before.

Due to anxiety, I had an oral HIV test completed 6 months later on 1/20/21 and a 4^th generation test on 02/03/21 (6.5 months). Both were negative. However, in the week prior to my oral test and the week prior to my 4^th generation tests I had received the first and second doses of the Moderna Covid vaccine.

My question is, If I did have Covid-19 could that extend the window period past the 45-day window period or cause a false negative test? In addition, could the vaccine have caused a false negative HIV test? I have read that HIV and Sars-Cov-2 have similar structure, I was wondering if this could affect antigen or antibody levels in the blood and affect testing.

Welcome to our forum and thanks for your confidence in an hour advice. Before I address your questions about COVID-19 and HIV testing let me provide a little information about Ureaplasma. Ureaplasma is part of the normal bacteria found in the genital track of both men and women. It is not considered a pathogen. Many years ago there was concerned that Ureaplasma might be causing STI‘s but that data has been disproven. Treatment of Ureaplasma is not typically recommended and when it is attempted it is commonly unsuccessful.  If your doxycycline treatment eliminated the Ureaplasma from your specimens that’s fine but should it appear again I would not be concerned that it was an STI and would recommend against treatment.---

Thank you for the explaining ureaplasma. I had actually never heard of it before. My doctor said he just routinely tests for it now since he has had multiple male patients have negative urine cultures, chlamydia, and gonnnorhea tests with STI symptoms that didn’t completely resolve with azithromycin/ceftriaxone shot. For me the ureaplasma came back positive and my symptoms did completely resolve with 2 weeks of doxycycline and I have since tested negative for ureaplasma twice. 

Correct, your HIV tests are entirely conclusive.  You can feel comfortable that you do not pose a threat to your new partner. EWH ---

As a current medical student I want to thank you for the information you have provided. As a future medical professional and as at home kits become more and more of the normal. When can a patient feel confident in their result or do you advise all patients to have a test on blood if possible. It seems that typically the 3 months is considered conclusive. However, when I was at a local health clinic having my oral test done they mentioned 6 months to be "conclusive" with no blood tests. 

Thank you.  As health professionals we believe it is our responsibility to help out patients, or on this site, our clients, be able to make informed decisions.  This involves integrating the patient’s circumstances ( again, for this site, that means information about exposures, past history, etc.) with our knowledge of epidemiology, partner characteristics, test performance, etc. to assess the likelihood and consequences of testing.  In your circumstance, you’ll have to make the decision regarding whose advice to take.  In my opinion whomever suggested a further, 6 month test was being over conservative without considering the variables above.   I’m not a betting person but in this instance I’d be happy to make a large bet that any future result will only confirm that you were not infected by the exposures you describe above.  ---

Just did another oral test at 8 months and as you bet, it came back negative. Thank you for your help and your service. It really helped me get over this very anxiety inducing experience.