People are starting to visit nations that offer different COVID-19 vaccines than the ones they received at home as international travel restrictions loosen. Some travelers to the United States who were immunized abroad have “doubled up” with another COVID-19 vaccine made by a different manufacturer in recent months, according to Reuters.
These passengers were given vaccines with low reported efficacy under emergency use authorization in the United States in some circumstances, according to the paper, with some hoping for more potent protection from the extremely contagious delta variant of the new coronavirus. Others have gone to work or school and are concerned about meeting FDA-approved immunisation requirements.
Several Americans have begun to seek out more vaccine doses, including those made by different manufacturers. Outside of the United States, a few countries are pressing forward with second or third doses of COVID-19 vaccine developed by separate companies.
According to some experts, there may be more compelling reasons to mix and match COVID-19 shots than levelling up to a shot with greater efficiency. In a statement released on August 10, the World Health Organization advised that further research into the consequences of mixing multiple vaccines is still needed. Scientists are now investigating how people's immune responses alter whether they receive only one form of vaccine vs two types of immunisation. However, the method may help stretch scarce vaccination supplies and, in some cases, provide better immune protection.
“The reality is, when you have so many individuals vaccinated with half a dozen different types of vaccinations out there, mixing and matching is almost inevitable,” says Deborah Fuller, a vaccinologist at the University of Washington School of Medicine in Seattle. “It should be fine, and seeing these vaccines combined together might even be beneficial.”
Has it ever been attempted to mix and match vaccines?
Yes, although not usually on purpose.
According to Fuller, people are occasionally given doses of both the injectable and oral versions of the polio vaccination, which contain “killed” and “weakened” copies of the virus. It's also usual in the United States for people to receive different forms of the seasonal flu vaccine from year to year.
According to Kirsten E. Lyke, director of the Malaria Vaccine and Challenge Unit at the University of Maryland School of Medicine's Center for Vaccine Development and Global Health in Baltimore, deliberately mixing multiple vaccines created for the same illness is a hot field of research.
Lyke, who recently coauthored an editorial in Nature Medicine about mixing COVID-19 vaccines, says, “It is a tried-and-true approach that we do with vaccine testing all the time, but it hasn't gotten to primetime, where there is a licenced vaccine combination that intentionally has a mixed platform.”
Vaccine and immunology researchers have already looked into the technique, which is known as heterologous prime-boost, for ebola, TB, and other infectious illnesses. For decades, many research groups, including Fuller's, have been examining the consequences of purposely combining different types of HIV vaccine candidates. In clinical trials, one pairing not studied by Fuller's team reduced the rate of infection by 31%. Even this little level of protection against such a cunning virus was considered a significant achievement by scientists.
Vaccine and immunology researchers have already looked into the technique, which is known as heterologous prime-boost, for ebola, TB, and other infectious illnesses. For decades, many research groups, including Fuller's, have been examining the consequences of purposely combining different types of HIV vaccine candidates. In clinical trials, one pairing not studied by Fuller's team reduced the rate of infection by 31%. Even this little level of protection against such a cunning virus was considered a significant achievement by scientists.
Previous research on mixing vaccinations produced for other infectious diseases haven't found any safety concerns, according to Fuller. More study is needed to confirm if this is the case with COVID-19 vaccinations.
When you mix vaccines for the same disease, what happens to the immune system?
To stimulate the immune system, the COVID-19 vaccines in use today employ a variety of ways:-
mRNA vaccines, which incorporate bits of genetic material that code for the spike-shaped protein on the surface of SARS-CoV-2, are being developed by Moderna, Pfizer, and BioNTech. Others are known as viral vector vaccines, such as the ones produced by Johnson & Johnson, the University of Oxford, and AstraZeneca. In these images, the coronavirus genes are carried by a different type of virus that has been genetically modified. Others in use outside of the United States contain spike protein fragments or inactivated virus.
Fuller believes that combining two different types of vaccines will be more effective than combining two vaccines that follow the same core method. “We believe that some people are simply better at stimulating specific immune system arms than others,” he explains. “And when you combine them, they start to synergize and exploit all of our defenses.”
For example, adenovirus- appear to be particularly good at rousing T cells, which are white blood cells that serve a variety of activities, including killing infected cells and directing the immune response, as found in the Johnson & Johnson and AstraZeneca vaccines. Meanwhile, according to Lyke, mRNA vaccines are particularly effective at inducing the formation of antiviral antibodies.
“Could you get the best of both vaccines and get a really fantastic antibody response along with a really strong T cell response if you mixed the two?” she wonders. “How would that then effect vaccine efficacy?”
It's possible that this method would be especially advantageous to persons who are immunocompromised. “We do know that a third dose of an mRNA vaccine appears to pick up a significant number of people who didn't respond the first time,” Lyke says. “However, it's worth considering whether giving them a Johnson & Johnson dose would be an even more effective immunological trigger.”
Mixed dosage may also be useful for another reason, according to Fuller. After receiving a viral vector vaccine, such as Johnson & Johnson's COVID vaccination, a person's body begins to produce antibodies not just against the coronavirus spike protein but also against the virus that is carrying the coronavirus material, referred to as the vector.
“If you keep attempting to boost...people will eventually develop immunity to the vector, and that vaccination won't perform as well,” Fuller adds. “An mRNA vaccine does not create that prior immunity, so you can keep getting updated booster doses as needed to counteract the introduction of new variants.”
People who caught COVID-19 before getting vaccinated may have a different type of mixing. Shane Crotty, a researcher at the La Jolla Institute for Immunology in California, wrote in the journal Science in June that the shots can bolster the immune response in survivors who already have some level of immunity from their encounter with the virus, and possibly even offer a particularly potent kind of "hybrid immunity."
Lyke and her colleagues hope to provide some answers about the safety of mixing COVID-19 vaccines and how the practice affects the immune system. They’re collaborating with the National Institutes of Health to investigate what happens when people who were immunized with one of the three vaccines under emergency authorization in the United States receive booster shots from a different manufacturer.
“By the end of August or the beginning of September, we should have some data,” she says. She does warn, though, that their study won't be able to enroll nearly as many people as the initial clinical studies. “On a population level, we won't be able to claim, ‘This combination guarantees you 97 percent protection.”
What do we know about COVID-19 vaccinations when they're mixed together now?
Some European countries stopped using AstraZeneca's vaccine in March after it was related to rare incidences of blood clots. As a result, many persons who had received their initial dose were offered second doses by other manufacturers, sparking curiosity about the implications of mixing and matching.
In recent months, a number of reports have provided positive outcomes. Scientists from Spain's CombiVacS experiment concluded in May that those who receive the Pfizer shot after a first dose of AstraZeneca's vaccine create more antibodies than those who only get the AstraZeneca vaccine.
According to the findings of the Com-COV research in the United Kingdom, mixing the AstraZeneca and Pfizer vaccines may result in a higher immune response than two doses of the AstraZeneca vaccine. Participants who received two doses of the Pfizer vaccine produced the highest level of antibodies, while those who received an AstraZeneca vaccine followed by a Pfizer vaccine showed the most strong T cell response, according to the researchers. However, it is still unknown which method will be the most effective. When German researchers coupled the AstraZeneca vaccination with those from Pfizer or Moderna, they saw similar results.
Moderna and an experimental protein-based Novavax vaccine were added to the Com-COV study this spring. Meanwhile, scientists in the Philippines are studying the effects of combining CoronaVac, a Chinese vaccine that combines an inactivated version of the SARS-CoV-2 virus, with six other vaccinations. The combination of the single-dose version of Russia's Sputnik V (which was initially meant to utilise a different adenovirus vector for its first and second doses) and the AstraZeneca vaccine is also being investigated.
Although researchers in the Com-COV study noted higher symptoms like as chills and headaches in persons who received various vaccines, these modest studies haven't discovered any major side effects related with mixing vaccines.
Are there any countries that administer mixed-vaccine regimens?
According to Reuters, a number of countries are exploring or have opted to mix and combine COVID-19 vaccines.
Denmark, Italy, Canada, Vietnam, and South Korea are among the countries that use vaccines made by different manufacturers for the first and second shots in their regimens. Others are giving people who have already been fully inoculated with other vaccines an extra dosage of Pfizer or Moderna's vaccine. Cambodia, Germany, Turkey, and Indonesia are among them.
“There is a major problem with scarcity all over the world; we have to do a lot better if we want to eliminate those spots where COVID can get in and then replicate and develop these extremely severe variants,” Lyke says. “So any information that may help us extend the vaccination we have available in any way, or maximise the best approach to provide a booster, that's extremely wonderful knowledge to have.”
Due of concerns about decreasing immunity, the US government stated this week that it planned to make COVID-19 booster doses widely available (although this decision has been criticised as premature by some scientists). Booster doses of the Moderna and Pfizer vaccines for immunocompromised patients had already been approved by the Centers for Disease Control and Prevention. According to the CDC, if the mRNA vaccination product used for the first two doses is unavailable or unknown, either mRNA COVID-19 vaccine product can be used.
The COVID-19 delta variant vaccines currently available in the United States are quite successful at keeping people from becoming seriously ill or dying from it. Combining COVID-19 vaccinations, on the other hand, could be “the route to go to generate longer-term immunity to combat even future variations to come,” according to Fuller.
In the meanwhile, contacting folks who haven't been vaccinated is a more immediate worry.
“We can talk about boosters ‘til we’re blue in the face,” says Lyke. “But if half the country won’t even get their primary vaccine, we really need to do better in messaging and convincing people how safe it is.”
On mixing of Covid vaccine here in India what govt says
In the Rajya Sabha, Minister of State for Health Bharati Pravin Pawar stated that national expert organisations had yet to make a recommendation on mixing Covid-19 vaccinations.
"Covid-19 vaccinations have recently been produced. As a result, scientific evidence about vaccine mix-and-match research is still developing "Pawar responded in writing.
She said that the National Technical Advisory Group on Immunization or the National Expert Group on Vaccine Administration for Covid-19 has made no recommendation to mix and match the first and second dose of the regimen.
"There is no specific recommendation from the World Health Organization presently on mix and match of vaccines," the minister added.