Everything you need to know about mixing vaccines!

For almost 1 and a half years the world has been fighting against coronavirus. Many of us have lost our friends and family members in this deadly war against Covid. As the vaccine was invented it was a great sigh of relief. Now we are all facing a severe shortage of vaccines. As different brands of vaccines were launched, the most common query nowadays is ‘can I take vaccines of different brands for a second dose?’ This is called mixing of vaccines.

What is mix and match?

Mix and match is the term used in case of vaccines. If you have taken a vaccine for a disease and you need a second but at the second time the same brand is not available the other brand with similar technology can be used. This is called ‘mix and match’ or simply mixing of vaccines.

Everyone who is above 18 is to be vaccinated with covid vaccine and this has created a huge gap between supply and demand of covid vaccine. People are getting the first dose but when they go for the second they may find it difficult to get the same brand.

This has caused a huge problem and I doubt whether they can mix the vaccine?

How does vaccines work?

In very simple words vaccines train your immunity to fight the disease. Vaccines are basically of two types: live vaccines and inactivated vaccines.

Live vaccine when injected to you, it infects you like actual real virus. It starts producing proteins that are similar to original virus. Your immunity recognizes those proteins and fights with them. When the real infection with real virus occurs your trained immunity fights that real virus more effectively and protects you against disease. Only the difference is virus in live vaccines are similar viruses with no capacity to cause disease.

Inactivated vaccines on other hand contain similar proteins to real viruses or the entire virus in an inactivated form. Similarly it is when injected to you, your immunity recognizes it as foreign proteins and launches an immune fight against it. It trains your immunity but does not infect you like live vaccines.

This is the simplest explanation of the most complicated thing for you to understand.

Why not mix vaccines?

Theoretically it seems like a very simple explanation. You may feel what’s a big deal it’s just about training your immunity. If the vaccines of different brands do the same thing with you then why not to mix and match?

In practice when a vaccine is launched only one vaccine is studied for safety and efficacy. They vaccines of different brands may contain different contents and even if they bothe achieve the same end goal they may have slightly different style of work. 

It is not a good idea without the knowledge of the end outcome of doing so. If the data proves that mixing is beneficial or not at least harmful, then it can be applied practically. But this data which is evidence to support or refute the possibilities is to be gathered after extensive clinical trials in the community.

What happens after mixing vaccines?

Mixing of Covid vaccine has not been studied extensively yet. So everyone has very little information about it.

There are some possibilities which can occur with mixing the vaccines. They are as follows:

• The mix and match may produce the same immunity levels as that by 2 doses of the same brands.
• The mixing of vaccines may not achieve the same immune response as that achieved by the 2 doses of the same vaccines.
• The third and most feared possibility is mixing of vaccines may increase the possibility of adverse reactions making them totally unacceptable.
• Fourth possibility is mix and match does not produce any effects or side effects making vaccination campaigns totally useless.

In case of covid vaccines all these possibilities are yet to be examined. So nothing can be said about what happens after mixing vaccines of different brands.

Which countries allow mixing?

There are countries which have started studies about match and mix. Some countries are saying it is safe to mix Pfizer and astrazeneca vaccines but these studies are still in early phase.

No countries have yet announced mixing of vaccines to be safe to use on a mass scale.

Spain	Declared Pfizer vaccine second dose safe and effective after first dose of Astrazeneca
USA	Allows mixing of Pfizer/Biontech with moderna vaccines only in exceptional situations.
France	Recommends a second dose of mRNA vaccine to those who have received the first dose of Astrazeneca.  Yet the safety of doing so has not been evaluated.
Norway	It has announced that it will inoculate mRNA vaccine to those who have got the first dose of Astrazeneca.

From the above table it is clearly established that mixing of vaccines is yet not recommended on a mass scale. It is mostly allowed in exceptional cases.

Which countries are conducting studies on mix and match?

As we discussed earlier some countries are conducting trials regarding mix and match of the vaccines. Those countries are as follows:

China	Clinical trials on mixing CanSino biologics and Chongqing Zhifei Biological Products
Finland	Astrazeneca and other vaccines
South Korea	Astrazeneca and other vaccines
Spain	Declared Pfizer vaccine second dose safe and effective after first dose of Astrazeneca
UK	Oxford studies earlier Astrazeneca  and Pfizer mixing found it may cause some mild side effects in recipients.Novavax has announced that it will participate in conducting the mixing studies
Philippines	It has been announced to study effects on mixing vaccines. The trials will start with Chinese Sinopharm vaccine and other vaccine brands. The studies will start from June 2021 to complete by Nov 2022.

From the above table it seems not many studies yet were conducted on mixing of vaccines.

What will be the benefit if possible?

If the studies are conducted and they find that mixing of vaccination is safe following will be benefits for the mankind:

• Safety and efficacy: We will know exactly the safety and efficacy of the vaccines.
• About brands: We will get a clear idea about which brands vaccines can be mixed and which not.
• Doubts about vaccines: With these studies many doubts about mixing and about vaccinations itself will be solved.
• Side effect profiles: With these studies the side effect profiles after mixing the vaccine will be more clearly established.
• If mixing is possible we will have more options available to vaccinate the entire population of the world. World is dealing with intermittent shortage of vaccine brands.

What are current recommendations?

Currently barring a few exceptional situations no countries are recommending mix and match of vaccinations.

If you have got the first dose of the vaccine and not found it of the same brand for the second dose you are suggested to wait.

We yet do not know the safety, efficacy and side effect profile of the mixing of the vaccines. 

You are suggested to carry your protective shield that is social distancing, hand sanitizers and most importantly the masks.

Was it attempted previously?

There was no such a huge pandemic in the last 100 years. This time the entire world is under an ongoing pandemic. Sometime back similar efforts were made in the Ebola epidemic but it was not of that magnitude.

Does it increase side effects?

Does mixing of the vaccines for covid increase the side effect is the biggest worry in front of scientists and experts. This mystery is yet to be solved and needs more studies.

Does it increase the efficacy of vaccines?

Yet more studies are required to evaluate the efficacy after the mixing of the vaccines. We yet do not know about the efficacy after the mixing of the vaccines.

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