We shall be discussing few issues that are on the burner today.
• Quick Second Dose or a Delayed Second Dose: which is preferable ?
• Third booster Dose ?
• Cocktail of different jabs.
(Mixing and matching different Covid Vaccines)
…
Stretching vaccine supply
It seems the necessity to stretch the vaccine supply has mothered a new perspective in our war against the covid-19.
In time of vaccine shortage, various strategies have been explored to cover the maximum number of people.
Although the concept has started as a temporary solution to the mismatch in vaccine supply and demand in UK, has now produced some unexpected perspectives.
As the gap between two doses of one vaccine is increased, the long term protection doubles.
Various options are explored below.
Single dose :
If you split a course of two-dose vaccine into two courses of one-dose vaccine, you can double the number of people immunised. COVID-19 vaccines that are designed to be two-dose also offer significant protection after the first dose.
1️⃣ Delayed second dose
When there are not enough vaccine doses, you might want to give more people some degree of protection by delaying the second dose instead of giving a small number of people the full protection. This was the rationale behind the UK government’s decision to extend the interval between the two doses of A-Z jab to 12 week for all COVID-19 vaccines given in the UK.
Now we know that by delaying the second dose as much as 10 months, the ultimate protection is much *better and lasts longer.*
Con: – Protection conferred after one dose is in the range of 50%. This falls even further to less than 30% against the dreadful Delta variant. The only option is to get the second dose as quickly as possible to get some respectable degree of immunity against this most virulent variant.
2️⃣ Third booster Dose:
That brings us to the logical conclusion to the three dose schedule: two doses at 4 weeks interval followed by a booster at 6- 10 months.
But that will increase the vaccine demand by 150%.
3️⃣ Mix and match different Jabs
When the supplies of different COVID-19 vaccines are unstable and the distribution logistics are challenging, mixing and matching vaccines can offer some operational flexibility in times of uncertainty.
It is seen that different vaccines confer differing degree of protection against the variants. If you combine two different brands, technically we can resist more variants of concerns even future VOCs
The fastest way to end this pandemic and to reopen economies is to
start by
• protecting the highest risk populations everywhere.
• Sharing finite supply strategically to cover maximum people.
That is easier said than done.
Do we need a Booster for those already fully vaccinated ?
Any vaccine against a rapidly mutating virus is limited by two factors-
- The “natural waning” of vaccine immunity,
- New variants could emerge that might not be fully covered by the current vaccines
For example, the Flu vaccine.
The annual flu shots are actually boosters against the new variants. We have standardised a procedure for formulating the vaccine for the next year. The Flunet collects the genetic sequences of flu viruses circulating from October till March every year. The future vaccine for the successive year is planned from this data. The new vaccine remains valid for exactly one year. The process repeats again.
COVID-19 vaccines might one day be folded into annual flu shots.
when we shall have breakthrough infections of clinical significance, then booster doses would likely be recommended.
The mRNA technology behind the Pfizer-BioNTech and Moderna vaccines lends itself to rapid modifications of the vaccine as quickly as within 100 days.
Moderna has tried a new sequence of its vaccine that is effective against Alpha and beta variants.
Pfizer is testing booster against Delta variants.
So the Moral question remains:
Do we need more people to get vaccinated with the existing vaccines or Do we go after boosters against the variants for the already vaccinated fraction ?
Dr Ramakanta's Ideas 