Serum sickness-like reaction; generalized urticarial rash; Swelling of her joints; worsening arthralgia; High fever; This case was reported in a literature article and described the occurrence of serum sickness-like reaction in a 4-year-old female patient who received DTPa (DTaP vaccine) for prophylaxis.   Co-suspect products included MEASLES MUMPS RUBELLA for prophylaxis, LIVE VARICELLA VIRUS VACCINE (VARICELLA VACCINE) for prophylaxis and POLIOMYELITIS VACCINE INACTIVATED (INACTIVATED POLIO VACCINE) for prophylaxis.   On an unknown date, the patient received DTaP vaccine, MEASLES MUMPS RUBELLA, VARICELLA VACCINE and INACTIVATED POLIO VACCINE. On an unknown date, 6 days after receiving DTaP vaccine, the patient experienced serum sickness-like reaction (serious criteria hospitalization), generalized urticarial rash (serious criteria hospitalization), swollen joints (serious criteria hospitalization), arthralgia aggravated (serious criteria hospitalization) and fever (serious criteria hospitalization). The patient was treated with prednisolone, methylprednisolone and prednisone. On an unknown date, the outcome of the serum sickness-like reaction, generalized urticarial rash, swollen joints, arthralgia aggravated and fever were recovered/resolved.   The reporter considered the serum sickness-like reaction, generalized urticarial rash, swollen joints, arthralgia aggravated and fever to be related to DTaP vaccine.  Additional details were provided as follows: This case was reported in a literature article and described the occurrence of serum sickness-like reaction (SSLR) in a 4-years old female patient, who was vaccinated with unspecified diphtheria, tetanus, and pertussis (DTaP) vaccine (manufacturer unknown) for prophylaxis. No information on patient's medical history, family history, concurrent condition or concomitant medication was provided. On an unspecified date, the patient received unspecified diphtheria, tetanus, and pertussis (DTaP) vaccine, unspecified measles, mumps, and rubella (MMR) vaccine, unspecified varicella vaccine, and unspecified inactivated polio vaccine (IPV) vaccine (administration route and site unspecified, dosage unknown; batch number not provided for all). The age of vaccination was not provided but it could be 3 years or 4 years. On an unspecified date, 6 days after the vaccination, the patient developed a generalized urticarial rash with swelling of her joints. The patient was started on prednisolone by her pediatrician for presumed SSLR however the patient was subsequently admitted with high fevers and worsening arthralgia. Her CRP, procalcitonin and ESR were all elevated and her respiratory viral panel was positive for adenovirus. Her complement levels (C3, C4) were normal. IV methylprednisolone was started with dramatic improvement and resolution in symptomatology over the course of 48 hours. The patient was diagnosed with SSLR due to routine vaccinations and was discharged on a prednisone taper with instructions to space out vaccinations in the future to elicit the causal vaccine. This case has been considered as serious due to hospitalization. The author commented, "SSLR's are usually attributed to medications and self-resolve after discontinuation of the offending agent. SSLR due to MMR, varicella, DTaP, and IPV vaccinations have not yet been described in literature. Refractory or severe symptoms with high fever, debilitating arthralgias, and persistent urticaria can be treated with prednisone. If steroids are given early on when the rash develops, the progression of the arthralgias and arthritis can be reversed. Similarly, too quick a taper of steroids would prove to be inadequate treatment with symptom progression. Co-infections with viruses could potentially mask the diagnosis of SSLR if there is not a high index of suspicion."