key: cord-0747723-l8m9p248
authors: Choi, Won Suk; Cheong, Hee Jin
title: Should the COVID-19 Vaccine be Administered Simultaneously with Other Vaccines?
date: 2021-09-27
journal: Infect Chemother
DOI: 10.3947/ic.2021.0307
sha: eba161e4c938de00791eb238f413f64bd0b7f7ac
doc_id: 747723
cord_uid: l8m9p248

nan

https://icjournal.org

As the coronavirus disease-2019 (COVID-19) pandemic continues and evolves, guidelines for the usage of COVID-19 vaccines are being continuously revised based on the accumulation of data and experience with the vaccine. On August 30, 2021, the Korea Disease Control and Prevention Agency (KDCA) revised its guidelines to allow individuals to simultaneously receive the COVID-19 vaccine and other vaccines [1] . Previously, a 14-day window both before and after receiving the COVID-19 vaccine had been recommended. This standard was set after reviewing foreign guidelines, as data on appropriate intervals between vaccines against COVID-19 and other diseases were limited due to the COVID-19 vaccine's novelty. However, as the COVID-19 vaccine has been more widely used, data relating to its experience, effectiveness, and safety have accumulated both domestically and internationally. These data have shown that there is no specific scientific basis for mandating an interval between the COVID-19 vaccine and other vaccine products, indicating that the guideline can be revised. The revision was also important as influenza season approaches. Given the need for influenza vaccines, maintaining a 14-day interval between the COVID-19 and influenza vaccines would be difficult.

In this regard, what are the current guidelines in other countries? Different countries have different standards regarding the appropriate interval between the COVID-19 vaccine and other vaccines. In the United States, the Food and Drug Administration approved COVID-19 vaccination for those aged between 12 to 15 years in May 2020 and also revised the guidelines to allow for simultaneous administration of the COVID-19 vaccine with other vaccines [2] . However, since it is not known whether the reactogenicity for the COVID-19 vaccine would increase when it and other vaccines are simultaneously received, the guidelines recommended that the individual's situation be considered prior to simultaneous vaccination [3] . It was recommended that separate syringes be used for each vaccine during simultaneous inoculation and, if possible, for each vaccine to be administered on different arms, or to have at least a one-inch gap between vaccination locations if administered on the same arm. The American Academy of Pediatrics has also issued a statement of support for this adjusted guideline [4] .

In the United Kingdom, guidelines suggest that simultaneous vaccination can be done, but a seven-day interval before and after the administration of the live vaccine for shingles is recommended [5] . Canada, meanwhile, recommends maintaining at least a 28-day interval before administering another vaccine after the COVID-19 vaccine, and that the COVID-19 vaccine not be administered until at least 14 days after another vaccine has been received [6] . However, Canadian's guidelines state that simultaneous vaccination or reduction of the interval is possible depending on the individual situation. While the World Health Organization still recommends an inoculation interval of 14 days, it has stated that this guideline might be revised once sufficient data are obtained [7] .

There are two main reasons for maintaining a 14-day inoculation interval. First, during simultaneous vaccination, it is relatively easy to distinguish which vaccine is responsible for a localized adverse reaction, assuming that the vaccines are given at different locations, but determining which vaccine causes a systemic adverse reaction would be difficult. For vaccines that already have significant safety data accumulated, there are almost no restrictions on their simultaneous inoculation; since the influenza vaccine has been verified as safe, there seems to be no reason to prohibit simultaneous vaccination, assuming that the person being vaccinated is in stable health. Second, there are concerns that immunogenicity of vaccines could be partially degraded due to the interference effect from different immune responses elicited by different antigens after vaccination. However, it is rare for such theoretical possibilities to be proven in actual effects. If the expected effects exceed these concerns, there are advantages of simultaneous inoculation in terms of convenience and timeliness.

What is the progress of research on simultaneous inoculation with COVID-19 and other vaccines? While various studies have been conducted on the immunogenicity and safety aspects of simultaneous inoculation with other vaccines, like the influenza vaccine, no final conclusion has been drawn as of September 2021.

So what should we do at present? Despite the lack of data, considering the general principles of vaccination, the chances of a significant impact on preventive effects or incidence of adverse reactions during simultaneous vaccination against COVID-19 and other diseases are small. For high-risk groups, such as those with underlying medical conditions, it is not only the COVID-19 vaccine that is extremely important [8] ; the influenza and pneumococcal vaccines are also recommended. However, both domestic and international analyses have reflected a decreased vaccination rate for other diseases due to the COVID-19 pandemic. Therefore, it is advisable to create a vaccination plan which increases individuals' accessibility to be vaccinated, improving vaccination rates and ensuring that they continue to receive appropriate vaccinations according to their age and health condition. This will be beneficial in increasing the vaccination rates for COVID-19 and other diseases. However, the continuous issues that arise regarding adverse events after COVID-19 vaccination should be considered [9] . If the COVID-19 vaccine is administered simultaneously with other vaccines and adverse events occur, controversy may arise over which vaccine was the cause. Therefore, it is advisable to consider the current health of the person to be vaccinated, along with the characteristics of the vaccine to be administered, and all details should be fully explained to the patient before deciding on the simultaneous vaccination. In addition, since COVID-19related research is being rapidly conducted, constantly checking for the most recent results and revising vaccination guidelines as appropriate is advised.

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