From the Guidelines
Yes, a vaccine can be given on the same day as an intramuscular (IM) penicillin injection, as long as they are administered at different anatomical sites. This is supported by the Advisory Committee on Immunization Practices (ACIP) recommendations, which state that many commonly used vaccines can safely and effectively be administered simultaneously, i.e., on the same day, not at the same anatomic site 1. The key consideration is to minimize local reactions and discomfort by separating the injection sites. For example, if penicillin is given in one deltoid muscle, the vaccine could be administered in the opposite deltoid or in the vastus lateralis (thigh) muscle.
Some key points to consider when administering a vaccine and an IM penicillin injection on the same day include:
- The immune response to vaccines is not affected by concurrent antibiotic therapy, including penicillin, as antibiotics target bacteria while vaccines stimulate the immune system through different mechanisms.
- Simultaneous administration of vaccines is critical in certain situations, such as preparation for foreign travel, and when uncertainty exists that a person will return for further doses of vaccine 1.
- If the patient has a history of severe allergic reactions to penicillin, caution should be exercised, and the healthcare provider should be informed before any injections are given.
- Experimental evidence and extensive clinical experience have strengthened the scientific basis for administering vaccines simultaneously, and this practice is recommended by the ACIP and the American Academy of Family Physicians (AAFP) 1.
From the Research
Vaccine Administration with IM Penicillin Injection
- The administration of a vaccine on the same day as an intramuscular (IM) penicillin injection is a topic of interest, with several studies providing insights into the safety and effectiveness of vaccine coadministration 2.
- A study published in 2025 found that adult vaccine coadministration is safe for all assessed combinations, with most adverse events being mild to moderate and of short duration 2.
- However, there is limited information specifically addressing the administration of vaccines with IM penicillin injections.
Safety of Vaccine Coadministration
- Research suggests that vaccine coadministration is safe and effective, with benefits outweighing the risks 2.
- A systematic review and meta-analysis found that severe adverse reactions to benzathine penicillin G are rare, with a pooled incidence of 9.7 per 10,000 cases 3.
- The relationship between vaccines and antibiotic resistance has also been explored, with evidence suggesting that vaccines can reduce the emergence of antibiotic-resistant strains by decreasing antibiotic use 4, 5.
Considerations for Vaccine Administration
- While there is no direct evidence addressing the administration of vaccines with IM penicillin injections, the available research suggests that vaccine coadministration is generally safe and effective 2.
- However, it is essential to consider the potential risks and benefits of vaccine administration in individual cases, taking into account factors such as the specific vaccine and antibiotic being used, as well as the patient's medical history and current health status.
- A study published in 2023 found that pre-vaccination antibiotic use was associated with a higher risk of COVID-19 infection and adverse outcomes, highlighting the importance of careful consideration when administering vaccines and antibiotics 6.