COVID-19: What does a booster shot do, will it knock down Omicron?

In a nusthell, a booster shot helps "remind" the body's immune system about the virus it needs to defend against. This improves or gives the immune system a "boost".

In general, protection from vaccines "wane" over time, experts say. A tetanus booster, for example, is recommended every 10 years. On the other hand, a study published in the journal Nature recently shows compelling evidence that the risk of severe COVID drops by factor of 20 in "high-risk" older adults who received a "booster" shot.

Who should have the booster shots?

The study shows that Israelis above age 60 who received a third dose of a COVID-19 vaccine are much less likely to test positive for SARS-CoV-2 or to develop severe COVID-19 than those who have had only two jabs, according to the study published on September 15, 2021. Israel was the first country to widely adopt the booster. The booster drive has been credited in part for ending Israel's fourth wave. Several countries have also authorised booster shots for their citizens.

Is Omicron covered by booster shots?

Booster vaccines are not variant-specific at this point. In general, they can generate an immune response from the body against most known SARS-CoV-2 variants of concern. Some of the shots can be tailored to target new strains. Booster doses that offer protection against the Delta variant are still in trials.

That makes the race against variants tricky. Newer ones emerge with increasing regularity. Newer versions of a vaccine have to be designed, tested and approved before being shipped for inoculation. So it’s challenging to keep pace with new strains.

Omicron is a new strain. So none of the booster shots targets the latest strain. But a fully vaccinated person is better equipped to deal with Omicron or any other variant. All vaccines are effective in reducing the severity of COVID-19 infection, averting hospitalisation and preventing death. So booster jabs should work against Omicron, even at reduced efficacy.

Pfizer-BioNTech and Moderna have announced that they are working on boosters that will provide immunity against Omicron. Pfizer expects to ship them in 100 days.

Moderna CEO Stephan Bancel told the Financial Times on Tuesday: "There is no world, I think, where [the effectiveness] is the same level...we had with [the] Delta [variant]. I think it's going to be a material drop. I just don't know how much because we need to wait for the data. But all the scientists I've talked to ... are like, 'This is not going to be good'."

Much remains unknown about the Omicron variant, though scientists are racing to establish its severity, transmissibility and whether it "escapes" current vaccines.

What countries have authorised COVID booster shots today?

On Sunday (November 28, 2021), the UAE approved a COVID-19 vaccine booster dose for all fully-vaccinated adults aged 18 and above, 6 months after the second dose. The eligible categories include those who are fully vaccinated with the two doses of the Pfizer-BioNTech and Sputnik vaccine.

Following are the countries that deployed COVID-19 booster shots so far:

We're updating this list as information becomes available.

Is it possible to fight COVID without booster shots?

With evidence showing that the immunity levels wane 5-6 months after initial dosing, and continue to fall considerably post that, most immuno-compromised individuals may require prompt administration of these booster shots. As we have already seen, numerous countries have decided to fast-track the administration of booster shots, on top of full vaccination.

What factors must be considered in boosting defences against COVID?

Given the known anti-coronavirus tools available (intramuscular vaccines, COVID pills, upcoming intranasal shots), there are two key factors to consider: the threshold of antibodies in the general population and long-term protection.

New data show these may only be conferred through booster vaccinations at this point. Scientists now believe that given the efficacy decline in existing shots, repeat shots — or upgraded doses — would offer a much stronger defence against the virus and ensure the vulnerable population are immune-protected.

What’s the level of efficacy decline of existing shots?

A US Centers for Disease Control Prevention (CDC) case-control analysis of the mRNA-1273 vaccine showed a decline in efficacy from 93% to 92% — after 120 days from the completion of vaccination, in contrast to a decline from 91% to 77% for BNT162b2, the Lancet reported.

The journal also quoted a Kaiser Permanents population report which indicates that the effectiveness of the BNT162b2 (Pfizer) vaccine against the Delta (B.1.617.2) variant fell to 53% — 4 months after the second dose. However, effectiveness against admission to hospitals remained high at 93% up to 6 months. Other reports from Israel and Qatar indicate declining protection.

Should existing vaccines be tweaked? Do existing vaccines still work against the new known variants such as Omicron?

Although these reports strengthen the case for a booster dose of BNT162b2, there is no evidence yet to suggest breakthrough infections by Omicron variant leads to more severe cases. Global policies related to vaccines would certainly be influenced by the data given the new variant.

Health officials and experts have been monitoring the real-world performance of the COVID-19 vaccines to see how long protection lasts among vaccinated people, including the new variants. The mRNA vaccines continue to offer very strong protection against severe disease and death.

Dr Angelique Coetze, chair of the South African Medical Association, and one of their experts who discovered the Omicron variant, said: "Looking at the mildness of the symptoms, there is no reason for panicking, as we don't see severely ill patients".

South Africa has more than 35 per cent of the country already vaccinated, according to South Africa's Department of Health. It is way better off than many of the countries, where many have not reached a 2 per cent full vaccination rate for their citizens.

Coetze, while citing the "mild" and asymptomatic cases, caution that the situation "might change, going forward."

What do experts say about Omicron's transmissibility and ‘immune escape’ ability?

It's still too early to say, according to experts. What's clear now is that the variant is highly transmissible, with cases and hospitalisations rising six times already, though death is a lagging indicator. They also said the symptoms are different from Delta.

The thesis that "Omicron is mild" is driven by best hopes, not science. It has no basis in clinical data and peer-reviewed studies. It's more of a conjecture, or hope, instead of scientific fact backed by extensive clinical analysis.

Currently, there's no information to suggest symptoms associated with Omicron are severe, though initial infections reported were among university students — younger individuals who tend to have more mild disease.

On Monday (November 29, 2021), the WHO stated that the newly discovered variant is likely to spread internationally, thus posing a "very high" global risk where COVID-19 surges could have "severe consequences" in some areas.

Here's the latest list of countries where Omicron cases have been detected.

The UN agency, in technical advice to its 194 member states, urged them to accelerate vaccination of high-priority groups and to "ensure mitigation plans are in place" to maintain essential health services.

Further research is needed to better understand Omicron's potential to "escape protection" against immunity induced by vaccines and previous infections, the health body said, adding that more data was expected.

Experts cite that understanding the level of severity of Omicron will take days to several weeks. All variants of COVID-19, including the Delta variant that is dominant worldwide, can cause severe disease or death, in particular for the most vulnerable people.