First Real World Study Shows 2 Doses of Vaccine Not Enough Against Omicron

The study, conducted by scientists in the UK, also found that this gap can be closed with COVID vaccine boosters.

First Real World Study Shows 2 Doses of Vaccine Not Enough Against Omicron

Vaccine protection against symptomatic infection considerably decreases in the face of the new COVID variant of concern, Omicron, finds the first real world study of its kind.

However, the study has found that a third booster dose could help close this gap.

Researchers compare the vaccines' performance against Omicron to that against the Delta variant (still the most dominant COVID variant in the world) and found, "vaccine effectiveness against symptomatic disease with the Omicron variant is significantly lower than with the Delta variant."

The study, conducted by the UK Government is still in the preprint stage, and is yet to be peer reviewed.

Here's a run through of what the study found.


What the Study Found

Before we look at the findings of the study, here are some key points to know about the study.

  • The study used cases tested from 27 November onwards wherein the positive predictive value was above 80 percent.

  • S-gene sequencing found 581 symptomatic Omicron cases.

  • In the same period, 56,439 eligible Delta cases were identified and 130,867 test-negative individuals were chosen for the control group.

  • The study involved people who had received 2 primary doses of the AstraZeneca and Pfizer-BioNTech vaccines.

  • The Booster given for both primary doses was Pfizer-BioNTech.

In the case of those who were vaccinated with the Pfizer vaccine, the vaccine's protection against symptomatic infection dropped to between 34 -37 percent 15 weeks after the second dose—significantly lower than its performance against the Delta variant.

On the other hand, those who received 2 doses of AstraZeneca, showed an even heaver loss of vaccine protection against symptomatic disease from Omicron at the same 15 week mark.

Among those who received AstraZeneca as the primary course, a third Pfizer booster dose increased vaccine effectiveness to 71.4 percent, two weeks after the shot.

In the case of those who received primary doses of the Pfizer Vaccine, its effectiveness increased to 75.5 percent.

While the study authors conclude that greater coverage of booster doses will be required to pad up protection against infection and mild disease from the Omicron variant, they clarify that the primary doses continue to protect against severe illness and death.

"Although we cannot comment on protection against severe disease, booster doses of BNT162b2 (Pfizer-BioNTech)...are likely to offer even greater levels of protection against severe disease," they write.

Omicron vs Delta

Drawing a comparison between Omicron and previous significant variants, the researchers pointed to how Beta, Alpha and Delta, all resulted in a drop in vaccine protection, which could be effectively made up for with a third booster shot.

According to the scientists, Omicron could take over Delta as the most dominant COVID variant as early as mid-December given the rate at which it's spreading.

These findings are consistent with preliminary neutralisation data for the Omicron variant.

They go on to explain that South African and German studies, as well as unpublished data from the UK have found a 10-fold reduction in neutralising activity in those who have received 2 doses of the Pfizer vaccine compared to the Delta variant.

More studies will be needed to know how long the protection provided by the booster doses will last.

Boosters in India

At the moment, booster doses have not been approved by the health authorities in India, although Serum Institute of India (makers of Covishield COVID vaccine) has approached the DCGI (Drugs Control General of India) for the same.

The expert panel evaluating the application, however, have asked SII to submit addition trial data to justify the need for booste

Speaking to FIT for a previous article, Virologist, Dr Shahid Jameel said, "...for India I think the priority should be to get the two shots to the people who are eligible to get the two shots."

"But, if there’s one group of people who should get the boosters, that’s the healthcare workers," he added.

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