Thread by @swapneilparikh

In this thread I’m going to commit the cardinal scientific sin of oversimplification to try and explain vaccine, neutralizing antibodies and protection from infection/sickness/hospitalization/death

The numbers used here are to explain a concept and aren’t necessarily to scale
1/

Let’s imagine the virus can be killed by bullets.

These bullets are neutralizing antibodies - antibodies that neutralize (kill) the virus.

A few bullets will prevent death/hospitalization, more bullets will prevent illness, a lot of bullets may even prevent infection.
2/

When you get vaccinated against COVID-19 you have a gun loaded with bullets to destroy the virus (SARS-CoV-2)
These bullets are neutralizing antibodies (nAbs = bullets)
Eg.
OG SARS-CoV-2🇨🇳 was neutralized with 2 bullets
B.1.1.7🇬🇧 needed 4 bullets
B.1.351🇿🇦 needed 16 bullets
3/

Different vaccines give a different number of bullets

Eg

Pfizer, Moderna, Novavax vaccine 20 bullets

Past infection, AZ/COVISHILED/COVAXIN 10 bullets

But remember just 4 bullets maybe enough

Vaccines also form immune memory so we can make more bullets quickly if infected

4/

2 doses of COVISHIELD/COVAXIN may give 10 bullets

But 1 dose may give just 5 bullets

If you get exposed to OG SARS-CoV-2 (needs 2 bullets), B.1.1.7 (needs 4 bullets), you’re probably fine. You have enough bullets!

5/

Along comes B.1.351 (needs 16 bullets)
If you have 20 bullets😎
If you have 10 bullets🤧🤒
No vaccine ☠️🪦
Any vaccine > no vaccine, but mRNA vaccines appear better

Even if you have 2 bullets but have immune memory, you can make new bullets - may get sick but mild infection

6/

Along comes B.1.617.2🇮🇳
14 bullets😎=may never get infected or maybe just asymptomatic infection
6 bullets🤧🤒=may get mild infection
2 bullets🥵😭🫁may get moderately sick but you make new bullets quickly, so vaccine prevents death
No vaccine =no bullets= 🏥☠️🪦

7/

1 dose of vaccine may not give enough bullets (nAbs) to prevent mild infection but the vaccine may still protect from death!

The question is how many bullets does it take to prevent infection?

How many to prevent hospitalization/death?

How many bullets does B.1.617.2 need?

8/

Note : B.1.617.2 is a SARS-CoV-2 variant of concern that belongs to the lineage Indian scientists loving named “THE DOUBLE MUTANTZZZZZ” 🦠👻😱

According to new information form the UK, this variant of concern is more transmissible and has some degree of immune evasion.

9/

Good news is our existing vaccines are likely to continue to offer high protection from death.
Protection from hospitalization may decrease a little bit, don’t know yet.
Protection from symptomatic infection has decreased a lot for 1 dose & a little for 2 doses as well.
10/