COVID Vaccines : How Long It Protect

Two Minutes Read : COVID Vaccines : How Long It Protect ?

From our experience of vaccines of epidemic diseases, we have learnt that

 1. Measles shots are good for life, 

 2. chickenpox immunisations protect for 10 to 20 years, 

 3. For Flu we have to take shot every year.         4. tetanus jabs last a decade or more. 

But so far we know little that how long COVID-19 vaccines can protect us , and whether we really need Covid-19 boosters. 

The goal of any  vaccine is to provide the protection afforded by natural infection, but without the risk of serious illness or death.

A really good vaccine makes it so someone does not get infected even if they are exposed to the virus but not all vaccines are ideal.

The three tiers of defence a vaccine include full protection against infection and transmission; protection against serious illness and transmission; or protection against serious illness only.

The effectiveness depends on the magnitude of the immune response a vaccine induces, how fast the resulting antibodies decay, whether the virus or bacteria tend to mutate, and the location of the infection.

The threshold of protection is the level of immunity that’s sufficient to keep from getting sick. For every bug, it’s different, and even how it’s determined varies.

Basically, it’s levels of antibodies or neutralizing antibodies per milliliter of blood.

A threshold for measles was pinned down in 1985 after a college dorm was ex- posed to the disease shortly after a blood drive. Researchers checked antibody concen-trations in the students’ blood donations and identified 0.02 international units per milliliter as the level needed to prevent infection.

You track antibody decline over time, and if you know the threshold of protection, you can calculate durability of protection. With Covid, we don’t know.”

Historically, the most effective vaccines have used replicating viruses, which essentially elicit lifelong immunity. Measles and chickenpox vaccines use replicating viruses.

Non-replicating vaccines and protein-based vaccines (such as the one for tetanus) don’t last as long, but their effectiveness can be enhanced with the addition of an adjuvant—a substance that enhances the magnitude of the response.

Tetanus and hepatitis A vaccines use an adjuvant.

AstraZeneca or Covishield  and the Johnson & Johnson Covid-19 vaccines use non-replicating adenovirus and don’t contain an adjuvant. The Pfizer and Moderna messenger RNA Covid-19 vaccines, which work differently, don’t contain any virus at all.

Complicating things further, viruses and bacteria that mutate to escape the body’s immune response are harder to control.

but at least eight variants of SARS-CoV-2, the virus that causes Covid-19, have been found. 

It does make it more complicated for the vaccine to work. You’re chasing multiple targets over time. 

Flu also mutates. But with flu, we’ve adjusted by making a new flu vaccine each year that as closely as possible matches the new strain of flu.

That is why Flu vaccines can offer protection for at least six months.

Setting aside the complexities of crafting an effective vaccine to combat a shape- shifting virus, some hope has revolved around the possibility of defeating Covid-19 by vaccines combined with the antibodies’ rates of decay produce durable immune responses.

Another way can be allowing to achieve  herd immunity, but the way coronaviruses infect the body makes that challenging.

Vaccines are very unlikely to lead to long-lasting herd immunity for many respiratory infections.The herd immunity only lasts for a modest period of time. It depends on how fast the virus changes. It depends on how fast the immunity wanes.

Part of the problem is that coronaviruses replicate in both the upper and lower respiratory tracts.

We have good circulation in our lungs and body, but not on the surfaces of our nostrils. We can block severe disease be- cause there are antibodies in the lower respiratory tract.But the risk of low-level infections in the upper respiratory tract can persist.

So what can be the way forward to combat COVID19. We have no choice but to update the vaccines to effectively combat variants of the virus, and the next generation of vaccines have also to focus on enhancing immunity in the moist surfaces of the nose and lungs.