Chicken pox 02

7 Things you need to know about Chickenpox vaccination

Chickenpox or primary Varicella infection is a disease caused by the Varicella-zoster virus (VZV).

The VZV is the same virus that causes Shingles or herpes zoster, while both chickenpox and shingles are caused by the same virus, they are clinically distinct. Chicken pox is a primary infection of the VZV meaning it occurs when the individual is first exposed to the virus.

Shingles on the other hand is a reactivation of VZV, this happens in individuals who have already had chickenpox because after the resolution of the chicken pox, the VZV continues to lay dormant in the system. Understanding the distinction between the 2 forms of varicella infection is important because the vaccine against Chickenpox is not the same as the one for Shingles.

Stages Of Infection

The natural history of a chicken pox infection can be thought of in 3 stages – viral prodrome, eruption of vesicular rash and resolution of rash. From the point of infection, it takes about 2 weeks before the distinctive vesicular rash of chickenpox appears. During these 2 weeks, individuals report prodromal symptoms of malaise, sore throat, loss of appetite and fever. The eruption of fluid filled vesicles generally starts after 2 weeks and stops within 4 days. The rash mostly starts at the face and progresses to the trunk and then to the extremities.  After another 6 days, the lesions will crust over and “shed’ off the body. The clinical manifestations of chickenpox tend to be milder in children but more complicated in adolescents, adults and immunocompromised individuals.

The chickenpox vaccine is a Live Attenuated Vaccine. This means that the vaccine was made with an inactivated form of the VZV. This form of vaccine is almost akin to getting a natural infection but in a controlled manner. Once this inactivated VZV is introduced into the system, the immune system is able to gradually build antibodies against a true form of the VZV thus allowing the body to fend off any further VZV infections.

While there are studies that recommend universal varicella vaccination, there are some groups that can be seen as a priority. These groups include teachers exposed to young children, non-pregnant women of child bearing age and healthcare workers. This is particularly the case if individuals are shown to not have any antibodies against VZV – which means they either have not had chicken pox before or have not had a vaccine against VZV.

The vaccine is given in 2 doses, 4 – 8 weeks apart and is generally well tolerated.

Common Side Effects

Common side effects include fever, injection site pain and vesicular rash around the injection site. Because Chickenpox vaccine is a Live Attenuated Vaccine, it should not be given to immunocompromised individuals – undergoing chemotherapy, on immunosuppressants such transplant patients or HIV patients with a low CD4 (Cluster of Differentiation 4) count. Particularly for HIV patients, it is important that the CD 4 count be consistently above 200 cell/uL with appropriate viral suppression, the 2 doses should also be separated by 12 weeks in HIV patients.

In summary, the chickenpox vaccine is a safe and effective means of preventing a primary VZV infection. The vaccine should be considered in women planning to get pregnant and adults who work in facilities with populations likely to transmit the virus – childcare, schools, hospitals especially if they have not had chickenpox before.


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