Photo by Mohammad Shahhosseini on Unsplash

Here’s a summary of Covid-19 variants and also vaccine efficacy for most of the top vaccines in use against the two main variants.

(sources used for this article list below)
(first published 11/06/21, updated 26/07/21)

VARIANTS on SARS Cov-2 (Wuhan), Dec. 2019

EPSILON — B.1.427/B.1.429 (USA) March 2020
ZETA — P2 — Brazil April 2020
BETA — B1351 (South Africa) May. 2020
ALPHA — B117 (UK) First detected — Sept. 2020
KAPPA B.1.617 (India) October 2020
DELTA B1617.2 (India) Oct. 2020
GAMMA — P1 (Brazil) Nov. 2020
IOTA B.1.526 (USA) Nov 2020
ETA — B.1.525 (various) Dec 2020
THETA — P3 (Philippines) Jan 2021

Delta is 40–64% more transmissible than Alpha and requires 83% of a population to be immunized to achieve herd immunity. In Thailand, 8% of infections are the Delta variant, while in the UK the figure is 96%, and the UK is expected to extend its lockdown rules. One third of UK patients infected with Delta ended up in hospital, despite having received their first dose of a vaccine, revealing the variant’s resistance to vaccine. To date 61.5% of the UK has received a first dose, and 43.7% a second dose.

The Alpha variant is also more transmissible than the original virus, but less so than the Delta, and requires 75% of the population to be vaccination to achieve herd immunity. It’s the dominant strain in Thailand (88% of infections).

The Beta variant has begun to emerge in some places as a concern and has been noted as “somewhat resistant” to vaccines, although the variant is also less transmissible.



Note that all vaccines provide very high (90–100%) protection from the need to be hospitalized or death, so the focus here is on data related to how well the vaccines provide protection against symptoms, or infection.

Vaccines & the Alpha Variant
Astra Zeneca — 74% against symptoms
Sinopharm — 73%,
Sinovac — ___61%,
Pfizer (mrna) 96%
J&J 72%, 72%
Moderna (mrna) — 94%,

Vaccines & the Delta Variant
AstraZeneaca — 35% against symptoms,(92% protection from hospitalization)
Sinovac (no data)
Sinopharm — 47% against symptoms
Pf izer— (updated 07/26 based on data from Israeli government) — 39% against infection, 40% against symptoms, 88% against hospitalization, 91% against severe Covid and death,
J&J 64% against symptoms
Moderna 89% against symptoms

Sinovac — There was no readily available data on its Delta efficacy. On the Gamma and Zeta variants, the WHO reported a 51% efficacy against symptoms ,100% against need for hospitalization, with no data on protection from infection.

There is evidence that a third shot of the AstraZeneca vaccine, given six months after the second dose, acts as an effective booster, including protection from the Beta variant.

Astra Zeneca Quality Control — The vaccines are approved by WHO. Siam Bioscience manufacturing facilities exist in Europe, and in Thailand. The Euro manufactured vaccines have been given approval by outside agencies. In regards, to vaccines made in their Thai facilities, “…samples from test batches of the COVID-19 vaccine made by Siam Bioscience (in Thailand) had passed the quality testing at AstraZeneca’s designated laboratories in Europe and in the U.S.

Sinopharm — the data is based on smaller sample sizes. The vaccine is easier to distribute as the cold storage requirements are less extreme, “Its easy storage requirements make it highly suitable for low-resource settings. It is the also first vaccine that will carry a vaccine vial monitor, a small sticker on the vaccine vials that change color as the vaccine is exposed to heat, letting health workers know whether the vaccine can be safely used.”





Educator, technology specialist, photographer, motorcyclist, and football enthusiast who also likes to write.

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Stephen Romary

Stephen Romary

Educator, technology specialist, photographer, motorcyclist, and football enthusiast who also likes to write.

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