Emb-175 first officer reported an near midair collision on approach to iah airport.

Attributes
ACN	1625351
Time
Date	201903
Local Time Of Day	1201-1800
Place
Locale Reference	IAH.Airport
State Reference	TX
Aircraft 1
Make Model Name	EMB ERJ 170/175 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	Vectors STAR GESSNR ONE
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Function	Pilot Flying First Officer
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 250 Flight Crew Total 4000 Flight Crew Type 520
Events
Anomaly	Conflict NMAC
Miss Distance	Vertical 300

Narrative:

While being vectored from the gessnr one to intercept the 8L localizer; with instructions to maintain an altitude of 3;000 feet MSL; we received a TA indicating a climbing intrusion 500 feet below; approaching from behind and crossing left to right. When the intruding aircraft was 400 feet below I received an RA 'do not descend' at this point I focused my attention to the pfd and anticipated a climb command.however; the intruding aircraft passed and there was no additional RA given and there was no deviation from the assigned flight path.after discussion with colleagues; we concluded that filing a report was not required due to the fact that we did not deviate from our assigned flight path. However; given that the aircraft encroached on our ATC assigned flight path; I felt it might be in the interests of safety to report.

Original NASA ASRS Text

Title: EMB-175 First Officer reported an NMAC on approach to IAH airport.

Narrative: While being vectored from the GESSNR One to intercept the 8L localizer; with instructions to maintain an altitude of 3;000 feet MSL; we received a TA indicating a climbing intrusion 500 feet below; approaching from behind and crossing left to right. When the intruding aircraft was 400 feet below I received an RA 'DO NOT DESCEND' at this point I focused my attention to the PFD and anticipated a climb command.However; the intruding aircraft passed and there was no additional RA given and there was no deviation from the assigned flight path.After discussion with colleagues; we concluded that filing a report was not required due to the fact that we did not deviate from our assigned flight path. However; given that the aircraft encroached on our ATC assigned flight path; I felt it might be in the interests of safety to report.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.