Dubai: Booster shots: do we need them?
The question is often asked around the world after a year of COVID-19 vaccinations. Now, countries including Israel, the UAE, the US, and the UK have already made their positions clear — booster jabs are encouraged, especially for those with compromised immune systems. In the UAE, federal government employees are mandated to take a booster dose.
How do boosters help?
Think of your booster shot, following two primary doses, as your best available line of defence against severe COVID. It activates B-cells and T-cells, armies of internal fighters in your body, to recognise and hunt down the enemy within. Vaccine boosters are found to be highly effective in warding off COVID-19 caused by Omicron, the new coronavirus variant of concern (VOC).
Although the strain has been around for over five weeks, several studies have found tha two-dose vaccines can reduce the impact of the highly-transmissible strain to a certain extent.
Boosters certainly push up the immunity levels. “The booster is exponential. It’s not just a little bit different. It’s a lot different,” Janet Hamilton, an epidemiologist and the executive director at Council of State and Territorial Epidemiologists, told US media.
Several studies — in Israel, Denmark, South Africa, Belgium, China, the US and the UK — all show the necessity of COVID boosters. As early as August 2021, an Israeli team showed a third Pfizer jab for over 60-year-olds offers up to six times greater protection from infection and serious illness after 10 days.
Israeli study
The Israeli study is significant: it backs the need for a booster shot to raise the wall of protection from severe illness, especially from the vulnerable or those whose immunity level drops signficantly (among those who have had only two doses), the Wall Street Journal reported. The data aligns with the results from a Pfizer study, which meant breakthrough infections (among the double-vaccinated) are a possibility.
With one boost, the increase in protection against Omicron jumped about a 100-fold, Israeli clinicians found. Among recipients of the third shot, no waning immunity was detected three months into the country’s booster drive.
With one boost, the increase in protection against Omicron jumped about a 100-fold, Israeli clinicians found. Among recipients of the third shot, no waning immunity was detected three months into the country’s booster drive.
UK studies
One UK study based on 581 people with Omicron shows a prior booster dose of Pfizer vaccine gave 70% protection against symptomatic infection for people who initially received AstraZeneca, and around 75% protection for those who received Pfizer as primary jab. The effectiveness of boosters against symptomatic infections of the Omicron variant, however, decreased in 10 weeks. This was confirmed by the UK Health Security Agency, citing initial findings from its real-world study.
In another UK research led by Prof Ravi Gupta at the University of Cambridge, his team investigated blood samples from vaccinated patients and found Omicron is able to evade vaccines, but less able to enter lung cells. Several other studies seemed to back the British findings.
Danish study
A study by a team in Denmark published recently analysed blood samples from 2,225 households with an Omicron infection. They found that booster-vaccinated people were 56% less likely to become infected compared to vaccinated people who had not received a booster.
More importantly, booster-vaccinated people were less likely to pass it on to others. At the same time, booster-vaccinated people were nearly 3.7 times more likely to get infected in the Omicron households than in the Delta households.
South African study
The South African study was based on 211,00 COVID-19 test results (78,000 attributed to Omicron) and released by South Africa’s National Institute for Communicable Diseases. It found that COVID-19 cases with Omicron are up to 80% less likely to be hospitalised.
Moreover, individuals who had received 2 doses of the Pfizer/BioNTech shot had a 70% chance of avoiding hospitalisation, down from 93% during the previous wave of Delta infections. In terms of avoiding infection altogether, however, vaccine efficacy dropped to 33%, from 80% previously.
Belgian study
Belgium’s Neyts Lab at Leuven University found similar results — markedly decreased viral load in lungs, replication and pathology — of Omicron in Syrian hamsters. Prof Johan Neyts said this may be because the virus was better at infecting humans than hamsters, or that it was more likely to infect the upper respiratory tract, or that it provoked less-severe disease.
Hong Kong study
And in Hong Kong, researchers have called for a third dose of vaccine after a study showed insufficient antibodies were generated by two vaccines to ward off Omicron.
Results of Moderna’s preliminary lab trials showed that its boosters significantly increased antibody levels against the newest variant. Other reports said the booster revved back the waning antibody levels by 25 times for Pfizer’s third shot and 37 times for Moderna’s.
What experts say
Virologist David Ho said studies based on real-world data showed that vaccine boosters provide 85% protection against severe COVID and eliminate the need for hospitalisation. “The real protection of the vaccine [booster] is largely against disease, and not against [the] acquisition of infection,” CNBC quoted the Columbia University professor as saying.
“Those who are vaccinated and boosted are largely going to do OK, even if infected. Those who are vaccinated and not boosted probably will have it slightly worse,” Ho added.
White House chief medical advisor Anthony Fauci also threw his weight behind vaccine boosters. “Our booster vaccine regimens work against Omicron. At this point, there is no need for a variant-specific booster,” he said.
Infectiousness
It's a fact: coronavirus is airborne. Mounting clinical data show Omicron is indeed so much more infectious than previous variants. One estimate made by George Washington University’s Dr Leana Wen shows Omicron now accounts for 95.4% of new COVID cases in the US.
But there’s a way to help protect yourself against symptomatic and severe illness: booster shots.
Prof. Ali H. Mokdad, former CDC senior epidemiologist and chief of Behavioral Risk Factor Surveillance System (BRFSS) of the agency, urges people to get their booster shots, in addition to wearing a good quality mask.
How much do booster shots protect against re-infection?
There are several lab and clinical studies on Omicron — all pointing to decreased lung cell infectivity.
The understanding of mechanisms at work in the immune system continues to improve, though it is still evolving.
Recent studies based on emerging real-world data show boosters provide roughly 75% to 85% protection against symptomatic Omicron infection, severe disease and hospitalisation, according to virologist Ho.
In short: Even if you test positive (from primary or secondary infection), you’re far less likely to experience COVID symptoms — particularly those severe enough to hospitalise or kill you — if you’re boosted. “The real protection of the vaccine [booster] is largely against disease, and not against acquisition of infection,” Ho says.
Which booster should you get, when will protection kick in and how long will it last?
Prof. Ho recommends an mRNA vaccine. Moderna’s booster is a higher dosage than Pfizer’s, but the results seem to be “quite similar,” he says. With mRNA vaccines, peak protection could be reached roughly two or three weeks post-booster. Over time, the antibodies you’ll gain from the booster will eventually wane — scientists are still working to learn how long your peak protection will last.
The Columbia University professor says early results show that a booster’s protection could wane at a similar rate to your second vaccine dose. “The waning that’s been seen so far (after the original two shot regimen), you would lose half your level by two months, so a half life of two months,” he says.
At some point, Ho says, you’ll probably need another booster shot, though he stresses it’s far too early to know what that extra dose’s timing will look like.
What does “decoupling” mean?
Experts use the term “decoupling” to refer to high infectiousness and lower death rate of Omicron, citing the studies which show it affects the upper respiratory tract more, which explains milder symptoms than previous variants — thus resulting in a "decoupling" in some places between soaring COVID case numbers and low death rates.
Prof. Monica Gandhi, an immunologist at the University of California in San Francisco, cites new studies and hints at the "silver lining" of the Omicron variant, i.e. that even as case numbers soar to records, the numbers of severe cases and hospitalisations have not. The data signal a new, less worrying chapter of the pandemic.
“We’re now in a totally different phase,” Gandhi told Bloomberg. “The virus is always going to be with us, but my hope is this variant causes so much immunity that it will quell the pandemic.”
The role of B-cells and T-cells vs COVID variants, including Omicron
T-cells activated by vaccines or prior COVID infection are seen behind the "durability of immunity" enough to fight Omicron. Could this explain the current lower hospitalisation rate (or the so-called "decoupling" between a huge spike cases and hospital admission) due to raised immunity, instead of a “milder" Omicron?
At least six studies from around the world reported this past week how T-cells, induced by multiple vaccines or prior COVID, hold up well against Omicron — exhibiting what is known as "cross-reactivity".
Researchers based in Singapore showed that 23 patients who recovered from the previous SARS pandemic (in 2003) still possess long-lasting memory T cells reactive to SARS-NP — a total of 17 years after the SARS outbreak.
This shows the "robust" cross-reactivity to SARS-CoV-2 neocapsid protein. And the researchers were startled to find out that, in 37 patients with no history of SARS or COVID-19, SARS-CoV-2 specific T-cells were also detected.
Specifically, the team studied T-cell responses to structural protein (known as nucleocapsid protein, NP) and non-structural protein (NSP-7 and NSP13 of ORF1) regions of SARS-CoV-2 in 36 people who recovered from COVID-19.
They found the presence of "CD4" and "CD8" T-cells recognising multiple regions of the neocapsid protein in SARS-CoV-2.
The coronavirus nucleocapsid is a structural protein that performs a number of functions and plays a key role in enhancing the efficiency of viral multiplication.
Renowned physician-scientist Prof. Eric Topol, founder and director of the US Scripps Research Translational Institute, said the new studies bolster the need for a booster shot.
They point to a well-preserved T-cell function (both CD4+ and CD8+ cell types), and their “durability” to fight off Omicron 6 to 8 months out from vaccination (using many types including Pfizer, Moderna, Astra-Zeneca, Novavax, J&J).
In a few of the reports, preserved T-cell function was seen after prior infection. In addition, memory B cells, after a 3rd shot, adapt with a subset that has high Omicron "cross-reactivity".
"This adds another line of defence to our immunity wall,” said Prof Topol. "Our smart immune system with multiple layers of defence and a virus with less intrinsic pathogenicity (Omicron) will help us win the latest variant battle,” he said.
