Bivalent COVID-19 vaccines contain two different components. One protects against the original strain of SARS-CoV-2, while the other protects against more recent variants.
SARS-CoV-2, the virus that causes COVID-19, continues to evolve over time. This has led to the continued emergence of new viral variants.
New variants differ significantly from the original strain of SARS-CoV-2 that was identified in 2019. For example, a 2022 review notes that, compared to the original strain of SARS-CoV-2, the Omicron variant carries
COVID-19 vaccines were developed based on the original strain of SARS-CoV-2. However, the continued evolution of the virus means that these original vaccines may not be as effective against newer variants.
To address this, updated COVID-19 bivalent vaccines were developed. These vaccines have a component that corresponds to the original strain of SARS-CoV-2 and one that corresponds to newer variants. Continue reading to discover more.
A COVID-19 bivalent vaccine has two different components. These provide two levels of protection.
The first component protects against the original strain of SARS-CoV-2. This is the component that was present in the original COVID-19 vaccines. It aims to provide broad protection against SARS-CoV-2.
The second component protects against more recent variants of SARS-CoV-2. This helps the COVID-19 vaccines keep pace with the continued evolution of the virus.
In addition to containing a component corresponding to the original strain of SARS-CoV-2, these vaccines also contained a component corresponding to the BA.4 and BA.5 lineages of the Omicron variant that were circulating at the time.
The original COVID-19 vaccines were monovalent. This means that they contained one component. Meanwhile, as we discussed earlier, the bivalent vaccines contain two components.
Overall, the side effects of the COVID-19 bivalent vaccine are similar to those of the original COVID-19 vaccine. Some of the most common side effects can include:
- pain, swelling, or redness at the injection site
- fever, with or without chills
- body aches and pains
- swollen lymph nodes
Side effects in young children may be:
- pain at the injection site
- increased sleepiness
- loss of appetite
- irritability or crying
- swollen lymph nodes
As with the original COVID-19 vaccine, side effects typically go away on their own in a few days. Serious side effects are rare and usually happen within 6 weeks of getting the vaccine, according to the
The COVID-19 bivalent vaccine is effective at protecting from serious illness and death due to COVID-19. However, the protection that it gives decreases in the weeks after it’s given.
One study, published in the New England Journal of Medicine in May 2023, included data from roughly a little over 1.2 million people who had received a COVID-19 bivalent booster. Its key findings were:
- The effectiveness against severe infection that resulted in hospitalization or death was:
- 67.4%, at 2 weeks after vaccination
- 47.5% after 4 weeks
- 44.3% after 10 weeks
- 38.4% after 20 weeks
- The bivalent vaccines provided similar protection for the Omicron BA.4 and BA.5 subvariants and subsequent Omicron subvariants like BQ.1 and XBB.
- The Moderna COVID-19 bivalent vaccine provided greater protection against infection than the one made by Pfizer-BioNTech.
- Protection against infection was higher in people who had previously had COVID-19 compared to those who had never had COVID-19.
It found that vaccine effectiveness was 72% and 68% for hospitalization and death, respectively. Additionally, those who got the bivalent booster had a lower rate of COVID-related hospitalization over 120 days than those who did not get it.
Children under 6 years old who received the original COVID-19 vaccine can also get the COVID-19 bivalent vaccine. The number of doses used depends on the type of vaccine and number of doses they originally received, as well as age.
Some individuals may get a second dose of the COVID-19 bivalent vaccine. This includes:
- adults ages 65 years and older: recommended time frame is 4 or more months after their first dose of the COVID-19 bivalent vaccine
- individuals who have a moderately or severely weakened immune system: recommended time frame is 2 or more months after their first dose of the COVID-19 bivalent vaccine
Can you get the COVID-19 bivalent vaccine if you didn’t get the original COVID-19 vaccine?
As of April 2023, the original monovalent COVID-19 vaccines are
- People ages 6 years and older will get one dose of the COVID-19 bivalent vaccine.
- Children younger than 6 years old will receive:
- a series of 2–3 doses if they’re between ages 6 months and 4 years
- a series of 1–2 doses if they’re 5 years old
- Those who are moderately or severely immunocompromised will receive three doses of the COVID-19 bivalent vaccine.
Updated COVID-19 vaccines in 2023 won’t be bivalent
In June 2023, the FDA
This new vaccine will target the XBB lineage of the Omicron variant, specifically the XBB.1.5 variant. Currently, the XBB.1.5 variant is declining in prevalence, while the presence of other variants, such as the EG.5 (Eris) variant, is increasing.
However, vaccine manufacturers expect that the updated vaccines will still give good protection. For example, Moderna recently announced that its updated vaccine increased the number of neutralizing antibodies to currently circulating strains like Eris.
COVID-19 bivalent vaccines contain two components. One protects against the original strain of SARS-CoV-2, while the other protects against more recent Omicron subvariants.
The COVID-19 bivalent vaccine effectively protects against serious illness or death due to COVID-19, although protection wanes with time. Its side effects are similar to the original monovalent vaccine.
Currently, everyone who is eligible for a COVID-19 vaccine can receive the bivalent COVID-19 if they haven’t already. The updated COVID-19 vaccines that will be available in the fall of 2023 will be monovalent.