Up until recently, there have not been any significant guidelines provided by the CDC, regarding mix regarding mix and matching of COVID-19 vaccines. Now the situation appears to be changing and greater clarity is available on booster doses for the COVID-19 virus. Fortifying an individual’s immunity by  booster whether by using the same or primary series of vaccine received earlier is called “homologous boosting” and if this increase in immunity is achieved by using a different type of vaccine, the process is called “heterologous boosting”.

Importance of booster doses has now been proven by studies. It is now accepted fact that booster vaccine doses tend to increase the antibodies response in an individual and is useful in protecting against newer variants as they emerge. Getting a booster vaccine aids in developing stronger immunity against different variants.


How many doses of booster vaccine do I need to take?

No definite guidelines have been published with regards to number of doses for booster vaccine. However, Covid vaccine booster doses are recommended to all high-risk population after 6 months of the last dose received as well as to those non high-risk populations who have completed 6 months from completion of their primary vaccination.


Who is eligible for booster vaccine?

To simplify, any one above 65 years of age who has completed their 6 months from their primary series of vaccination, as well as those ages 18 and above who are at high risk of Covid infections due to some underlying condition, those who are immunosuppressed or working in health care facilities may receive booster after completion of 6 months from their primary series.


Here to share some information of types of Covid Vaccine

Types of Covid vaccine:

There are 4 different types of Covid Vaccine approved. Each of these stimulates body’s immune response to generate antibodies against Covid-19.

Whole Virus: Here the whole virus after being inactivated, is administered to a patient to help protect them. Because the virus is not active, it will not cause disease after it is injected into the body. After being injected the body generates a robust immune response to this antigen or protein structure of the virus. The immunity generated helps protect an individual from severity of the disease if they are exposed to the live virus.

Viral Vector: This type of vaccination uses some genetic code from the targeted virus placed into a harmless virus called “vector virus”. Once injected into the body, our cells take up this genetic information to produce antigen or a protein code, towards which our immune system reacts and develops antibodies. This happens without a patient experiencing the symptoms of disease

mRNA vaccines: these vaccines also use genetic codes to insert into our body’s own cells to produce antigen which triggers our immune system to produce antibodies and hence create an ability to fight against the live virus should it be encountered at a future time.


Subunit vaccines:  In this situation some portion of the virus protein is used as the antigen and is injected into the body to help the body mount an antibody or protective response without creating the actual symptoms of the disease.


Types of Covid Vaccine and their doses

Pfizer mRNA


2 doses Available in Pakistan
Moderna mRNA


2 doses Available in Pakistan
Sinopharm Whole inactivated virus 2 doses Available in Pakistan
Sinovac / Pakvac Whole inactivated virus 2 doses Available in Pakistan
AstraZeneca-Oxford Viral vector


2 doses Available in Pakistan
Sputnik Viral vector


2 doses


Available in Pakistan
J & J Viral vector 1 dose Not available in Pakistan
CanSino Viral vector 2 doses Available in Pakistan



Whether a vaccine is an mRNA vaccine or an inactivated vaccine, studies have proven that Covid-19 vaccines have shown to bring not only a decline in the number of cases, but very importantly, a very significant reduction in the severity of the illness leading to a reduction in hospital admission.

For the booster shots, especially if an inactivated virus has been administered, the approach of “Mix and Match”, is recommended, using a mRNA or viral vector vaccine, because each vaccine have different methods of generating body’s own immune response and may be able to help with augmenting immunity. Receiving a vaccine via a more robust and different technology may help in generating a greater boost in the immunity.