UWorld Step 2 id:20700 says that "patients may develop recurrent symptoms 5-14 days after each dose of [chimeric monoclonal antibodies]."
Additionally, AMBOSS does not support a specific 7-10 day timeline, and rather states, "Symptoms appear 1–3 weeks following initial exposure (because antibodies take several days to form) and typically resolve within a few weeks after discontinuation of the offending agent."
FA25 pg 111 also says "Fever, urticaria, arthralgia, proteinuria, lymphadenopathy occur 1–2 weeks after antigen exposure."
Source: AMBOSS - https://next.amboss.com/us/article/Vt0Gc3?utm_source=amboss-anki-deck-template-script&utm_medium=anki&utm_campaign=amboss-anki-deck-template-script-beta&utm_term=serum+sickness&aid=298bfc66-b119-4c76-b7ef-8bfc7d192ab2&uid=ptfeLeLy0#Za175872da7e10019b960c6b80f28b3ba