Is it safe to mix vaccines?
Is it safe to mix vaccines?
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Aug. 11, 2021: With the emergence of the highly transmissible COVID-19 delta variant, more and more COVID-19 vaccine combinations have been reported, especially with many people taking a booster dose of an mRNA vaccine (Pfizer or Moderna) after the single dose of the Johnson & Johnson’s Janssen vaccine. Several countries in Europe followed up their AstraZeneca shots with Pfizer/ BioNTech or Moderna vaccines. The immune response in patients who received mixed doses seems to be strong, according to available data.
Aug. 11, 2021: With the emergence of the highly transmissible COVID-19 delta variant, more and more COVID-19 vaccine combinations have been reported, especially with many people taking a booster dose of an mRNA vaccine (Pfizer or Moderna) after the single dose of the Johnson & Johnson’s Janssen vaccine. Several countries in Europe followed up their AstraZeneca shots with Pfizer/ BioNTech or Moderna vaccines. The immune response in patients who received mixed doses seems to be strong, according to available data.
Recent studies suggest that mix-and-matching vaccines for a booster is safe and effective, and could even potentially enhance immunity. One can also mix shots for a first dose depending on the vaccines available. The World Health Organization (WHO) stance is that you should take whichever WHO-approved vaccine is made available to you first, and that it is safe and effective to mix-and-match different WHO-approved COVID-19 vaccines.
Recent studies suggest that mix-and-matching vaccines for a booster is safe and effective, and could even potentially enhance immunity. One can also mix shots for a first dose depending on the vaccines available. The World Health Organization (WHO) stance is that you should take whichever WHO-approved vaccine is made available to you first, and that it is safe and effective to mix-and-match different WHO-approved COVID-19 vaccines.
Publication
What our experts say
Recent data has led a number of health bodies, including the WHO, to endorse the use of mixed vaccines and mixed boosters. Someone can get a booster that is a different brand than their original shot, and can also mix brands for first and second doses, depending on the vaccines available.
World Health Organization (WHO) guidance says people should take whichever vaccine is made available to them first, and that it is safe and effective to mix-and-match different COVID-19 vaccines. This stance is based on studies researching the safety and efficacy of mix-and-matching different vaccines. It is a normal practice is many countries globally. Scientists believe mixing boosters could actually help enhance the immune system's response to the COVID-19 virus and potentially obtain more protection against severe symptoms, hospitalizations, and deaths as a result of infection.
The WHO's Strategic Advisory Group of Experts (SAGE) suggested that people who have received two shots of Sinovac or Sinopharm can use a Pfizer or AstraZeneca shot for their third dose. Studies have also demonstrated that using AstraZeneca's vaccine for the first two shots followed by an mRNA shot is another way to enhance protection. The U.S. CDC also now offers the ability for people who received one or two Johnson & Johnson shots for their initial vaccinations to substitute an mRNA vaccine for their booster.
Recent data has led a number of health bodies, including the WHO, to endorse the use of mixed vaccines and mixed boosters. Someone can get a booster that is a different brand than their original shot, and can also mix brands for first and second doses, depending on the vaccines available.
World Health Organization (WHO) guidance says people should take whichever vaccine is made available to them first, and that it is safe and effective to mix-and-match different COVID-19 vaccines. This stance is based on studies researching the safety and efficacy of mix-and-matching different vaccines. It is a normal practice is many countries globally. Scientists believe mixing boosters could actually help enhance the immune system's response to the COVID-19 virus and potentially obtain more protection against severe symptoms, hospitalizations, and deaths as a result of infection.
The WHO's Strategic Advisory Group of Experts (SAGE) suggested that people who have received two shots of Sinovac or Sinopharm can use a Pfizer or AstraZeneca shot for their third dose. Studies have also demonstrated that using AstraZeneca's vaccine for the first two shots followed by an mRNA shot is another way to enhance protection. The U.S. CDC also now offers the ability for people who received one or two Johnson & Johnson shots for their initial vaccinations to substitute an mRNA vaccine for their booster.
Context and background
There are more than ten COVID-19 vaccines being used around the globe now and 1.2 million doses have already been administered, but not all have been approved by the WHO and they may be unsafe to mix unless national health agencies have given guidance about specific combinations.
There are more than ten COVID-19 vaccines being used around the globe now and 1.2 million doses have already been administered, but not all have been approved by the WHO and they may be unsafe to mix unless national health agencies have given guidance about specific combinations.
Resources
- Interchangeability of Authorized COVID-19 Vaccines (Public Health Agency of Canada)
- PDF [465 KB] Figures Save Share Reprints Request Heterologous prime-boost COVID-19 vaccination: initial reactogenicity data (The Lancet)
- Mix-and-match COVID vaccines trigger potent immune response (Nature)
- Comparing COVID-19 Vaccine Schedule Combinations (University of Oxford)
- Heterologous prime-boost: breaking the protective immune response bottleneck of COVID-19 vaccine candidates (Emerging Microbes & Infections)
- Heterologous ChAdOx1 nCoV-19 and BNT162b2 prime-boost vaccination elicits potent neutralizing antibody responses and T cell reactivity (medRxiv)
- Canada recommends mixing and matching AstraZeneca, Pfizer and Moderna COVID-19 vaccines (CBC)
- Reactogenicity and Immunogenicity of BNT162b2 in Subjects Having Received a First Dose of ChAdOx1s: Initial Results of a Randomised, Adaptive, Phase 2 Trial (CombiVacS) (Preprints with The Lancet)
- Is it safe to mix and match COVID-19 vaccines? (Gavi: The Vaccine Alliance)
- Factbox: Countries weigh 'mix and match' COVID-19 vaccines (Reuters)
- Mixing COVID-19 vaccine doses leads to more reactions, study finds, which may be 'first sign of success' (CBC)
- Bahrain offers Pfizer booster for some who got Chinese shots (The Washington Post)
- Spanish study finds AstraZeneca vaccine followed by Pfizer dose is safe and effective (Reuters)
- Five things to know about: Mixing and matching coronavirus vaccines (Horizon: The EU Research & Innovation Magazine)
- FAQ: Where Do Countries Stand on Mixing Vaccines? Is It Safe? (The Quint)
- Philippines to study mixing Sinovac with other COVID vaccines (Nikkei Asia)
- COVID-19: You can now take Pfizer vaccine after two doses of Sinopharm in Abu Dhabi (Zawya by Refinitiv)
- Why mixing vaccines could help boost immunity (MIT Technology Review)
- CDC Recommends Additional Boosters for Certain Individuals (United States Centers for Disease Control and Prevention)
- Mixing and Matching COVID-19 Vaccine Booster Doses (United States National Institutes of Health)
- Episode #54 - COVID-19: Mixed and fractional vaccine doses (World Health Organization)
- COVID-19 advice for the public: Getting vaccinated (World Health Organization)
- Coronavirus disease (COVID-19): Vaccines safety (World Health Organization)
- WHO Experts Recommend Third Booster to Supplement Chinese Vaccines (Health Policy Watch)
- Interchangeability of Authorized COVID-19 Vaccines (Public Health Agency of Canada)
- PDF [465 KB] Figures Save Share Reprints Request Heterologous prime-boost COVID-19 vaccination: initial reactogenicity data (The Lancet)
- Mix-and-match COVID vaccines trigger potent immune response (Nature)
- Comparing COVID-19 Vaccine Schedule Combinations (University of Oxford)
- Heterologous prime-boost: breaking the protective immune response bottleneck of COVID-19 vaccine candidates (Emerging Microbes & Infections)
- Heterologous ChAdOx1 nCoV-19 and BNT162b2 prime-boost vaccination elicits potent neutralizing antibody responses and T cell reactivity (medRxiv)
- Canada recommends mixing and matching AstraZeneca, Pfizer and Moderna COVID-19 vaccines (CBC)
- Reactogenicity and Immunogenicity of BNT162b2 in Subjects Having Received a First Dose of ChAdOx1s: Initial Results of a Randomised, Adaptive, Phase 2 Trial (CombiVacS) (Preprints with The Lancet)
- Is it safe to mix and match COVID-19 vaccines? (Gavi: The Vaccine Alliance)
- Factbox: Countries weigh 'mix and match' COVID-19 vaccines (Reuters)
- Mixing COVID-19 vaccine doses leads to more reactions, study finds, which may be 'first sign of success' (CBC)
- Bahrain offers Pfizer booster for some who got Chinese shots (The Washington Post)
- Spanish study finds AstraZeneca vaccine followed by Pfizer dose is safe and effective (Reuters)
- Five things to know about: Mixing and matching coronavirus vaccines (Horizon: The EU Research & Innovation Magazine)
- FAQ: Where Do Countries Stand on Mixing Vaccines? Is It Safe? (The Quint)
- Philippines to study mixing Sinovac with other COVID vaccines (Nikkei Asia)
- COVID-19: You can now take Pfizer vaccine after two doses of Sinopharm in Abu Dhabi (Zawya by Refinitiv)
- Why mixing vaccines could help boost immunity (MIT Technology Review)
- CDC Recommends Additional Boosters for Certain Individuals (United States Centers for Disease Control and Prevention)
- Mixing and Matching COVID-19 Vaccine Booster Doses (United States National Institutes of Health)
- Episode #54 - COVID-19: Mixed and fractional vaccine doses (World Health Organization)
- COVID-19 advice for the public: Getting vaccinated (World Health Organization)
- Coronavirus disease (COVID-19): Vaccines safety (World Health Organization)
- WHO Experts Recommend Third Booster to Supplement Chinese Vaccines (Health Policy Watch)
