KINIGUIDE | It has been nearlya year since the Covid-19 Delta variant was first detected on Sept 7, 2020, andsubsequently took over the world by storm.
It proved fitter than all Covid-19 variants that came before, driving the outbreak in India in February and spreading to at least 132 countries acrossthe globe.
In that time, many painful lessons have been learned from thisdangerous new foe that had the US Centres for Disease Control (CDC)reckoning “the war has changed”.
While our understanding of the Delta variant is still evolving,this instalment of KiniGuide will attempt to sum up what we know so far.
What is the Delta variant?
The Delta variant (also known as B.1.617.2) is a variant of the SARS-CoV-2virus that is distinguished from other variants by several key mutations.
The variant was first sequenced on Sept 7 last year, but the significance ofthose mutations did not become clear until months later when it propelled theoutbreak in India that lasted from around mid-February until mid-May.
In recognition of the threat it poses, the World Health Organisation (WHO)flagged it for closer scrutiny by classifying it as a “variant of concern”(VOC) in May.
It is the most infectious Covid-19 variant yet, as well as being potentiallydeadlier than the original strain that was first detected in Wuhan, China.
In addition, while vaccines still offer protection against the variant, someof its original potency is lost when faced with this new threat.
How prevalent is it in Malaysia?
Health Ministry director-general Dr Noor Hisham Abdullah had said the Deltavariant is the dominant Covid-19 variant in the country, but so far, noestimate has been given on its prevalence.
The Health Ministry does regularly announce findings from its genomicsurveillance efforts, where genetic sequencing is used to identify the variantinvolved in certain Covid-19 cases.
In the latest update on July 28, NoorHisham said the Institute of Medical Research has sequenced 10 Covid-19 samplesfrom July 22 up to that date.
All samples turned out to be of the Delta variant.
This does not necessarily mean all Covid-19 cases in Malaysia are of theDelta variant, however, further analysis would be needed to make an estimatebased on the small number of Covid-19 samples that have been sequenced.
How infectious is it?
Estimates suggest that the Delta variant is 97 percent more infectious thanother variants that are neither classified as VOCs, or variants of interest(VOI), making it by far the most contagious variant yet.
For comparison, the same estimate published in the journalEurosurveillance last month says the highly contagious Alpha variant isonly 29 percent more infectious than non-VOI/VOC variants, and Beta is only 25percent more infectious.
Estimated change ineffective reproduction number of SARS-CoV-2 variants relative to non-variantsin 64 countries, data until June 3, 2021. Estimates for individual countries are marked in grey, while the pooled estimate for the Delta variant is marked in yellow.
Noor Hisham said the Delta variant has a basic reproduction number (R0) of between five and eight, meaning that every 100people infected with the variant would go on to infect between 500 and 800people. The cycle would then start afresh with a greater number of infectors tospread the disease.
It is understood that this particular scenario assumes apre-pandemic situation where no precautions were taken against the disease.
For comparison, the R0 during the outbreak in Wuhan last year prior to thecity’s lockdown was estimated to be around 2 to 2.5. Any number higher than1.00 indicates an outbreak that is growing faster and faster.
Malaysia’s latest effective reproduction number (Rt) - which accounts forprevention measures and immunity - is 1.07 as of Aug 2.
Meanwhile, Australian media highlighted a case of Delta variant transmissionat a Sydney shopping mall, where health authorities scrutinising the mall'sCCTV footage found the two strangers involved had only briefly crossed paths.
“We actually have CCTV footage of the encounter and it is basically acrossover of individuals. They are clearly facing each other but it isliterally someone moving across from each other for a moment, close, butmomentary,” New South Wales chief health officer Kerry Chant was quoted assaying by ABC.
The report did not mention whether the individuals were masked, which wasonly made mandatory several days later in response to the incident.
More recently, a study - which has yet to be formally vetted by otherexperts - found clues on how the Delta variant became so infectious.
Researchers reported that after close contact with a Covid-19 patient withthe Delta variant, the newly infected people would start testing positive forCovid-19 during RT-PCR tests around four days later, compared to around sixdays for cases studied in 2020.
Moreover, these individuals carried 1,260 times more of the virus in theirnoses and throats compared to those infected with earlier strains.
A pre-print of a study in Singapore not only found higher viral loads inDelta variant patients, but the viral load also remained elevated for 18 dayscompared to 13 days for non-VOC variants.
In other words, people who get infected with the Delta variant may becomecontagious sooner, and when they do, they may be shedding more viral particlesinto their surroundings and for longer periods of time – if the findings ofthese studies are validated in further studies.
Even fully vaccinated people are not spared. While they are less likely tobecome infected in the first place, it appears that they could become ascontagious as unvaccinated people once an infection takes hold.
According to a report published in CDC’s 'Morbidity and Mortality Weekly Report' on Friday, fully vaccinated people hadviral loads just as high as people who are unvaccinated or only partiallyvaccinated.
This is in stark contrast to earlier studies involving other variants, whereeven partially vaccinated people are found to be less likely to spread Covid-19if they become infected.
The revelation has prompted the CDC to backtrack on its relaxed masking recommendations forfully vaccinated people and advocate universal masking.
Is the Delta variant more dangerous?
Yes, and in more ways than one. The fact that it is more contagious means itis more likely to overwhelm healthcare systems.
This alone will cause the quality of care to deteriorate for everyone in the event of an outbreak – for those with Covid-19 or not.
Meanwhile, several studies have found that the Delta variant is associatedwith increased risk of hospitalisation, ICU admission, and death; thoughestimates vary on the extent of this increase.
The following estimates should be considered preliminary due to the smallsize of each study and many have not undergone peer review:
Health authorities in England estimated a 126 percent increasein the risk of requiring hospitalisation with the Delta variant compared to theAlpha variant, within 14 days of testing positive.
In Scotland, the risk ofhospitalisation is estimated to be 85 percent higher compared to the Alphavariant.
In Singapore, the Delta variant is estimated to be 88percent more likely to result in supplementary oxygen requirement, ICUadmission, or death compared to non-VOC variants.
In Canada, the variant is associatedwith a 120 percent increase in hospitalisation risk, 287 percent increase inICU admission risk, and 137 percent increase in the risk of death; compared tonon-VOCs.
How do we prevent it?
The methods of preventing Covid-19 infection has not changed much since the advent of the Delta variant, even though the virus is now better adapted toexploit any gaps in these defences.
These measures include physical distancing, masking, frequent handwashingand good ventilation.
Physical distancing of one metre or more can reduce exposure to the virus,while good ventilation prevents the virus from accumulating in indoor spaceswhere it could linger for hours.
The Occupational Safety and Health Department (Dosh) has released guidelines urging buildingmanagers of public areas to “maximise ventilation” and “minimise indoor airrecirculation”. Guidelines have also been issued for residential, non-residential, and healthcare facilities.
Meanwhile, WHO recommended a ventilation rate of 10 litres persecond for each occupant in the room, failing which, the shortfall should bemade up using several strategies including standalone airfilters.
The WHO also recommends slightly higher quality air filters than thoserecommended by Dosh, stipulating the MERV 14 standard instead of the MERV13.
Meanwhile, proper masking will stilllimit the number of infectiousparticles spread by infected persons, which is particularly important sinceeven asymptomatic individuals can be infectious and may not be aware theyare a danger to others.
It also reduces healthy individuals’ exposure to infectious particles byfiltering the air.
The US CDC has been recommending higher quality maskssuch as those meeting the KN95 standard, but continue to insist thegold-standard N95 masks should be reserved for healthcare workers.
It also recommended several ways to improve the fit of surgical masks, such as by wearing a cloth mask over it to seal its edges and improve fit, by tucking in its sides, or by wearing a mask brace.
When all else fails, vaccines help ensure that the body’s last line of defence will be able to mount a swift and effective response against the virus.
How well do vaccines work against the Deltavariant?
When it comes to the prevention of all Covid-19 symptoms, vaccines generallyhave slightly reduced effectiveness against the Delta variant compared tonon-VOC strains but the remaining protection is still significant.
Moreover, vaccines still retain much of their original potency when it comesto preventing Covid-19’s worst outcomes – hospitalisation and death.
For the Pfizer vaccine, studies in Canada, England and Scotland have come up withestimates varying from 83 percent to 88 percent protection against symptomaticinfection. Israel is an outlier in this respect,with a much lower estimate of 64 percent.
Nevertheless, the Israeli Health Ministry said the vaccine remains 93percent effective in preventing serious illness and hospitalisation, whilePublic Health England (PHE)estimated it to be 96 percent.
For the AstraZeneca vaccine, PHE estimated it to be 67 percent effectiveagainst Delta variant symptoms and 92 percent against hospitalisation, whileits Scottish counterpart estimated it to provide 61 percentprotection against symptomatic infection.
No data is available yet for the Sinovac vaccine’s effectiveness against the Deltavariant, but the company assured that it is still effective.
“It was more than 90 percent effective against severe infection andhospitalisation. We also noticed that the infection rate after vaccination hasbeen very low in these countries, and the symptoms too very mild in mostcircumstances," a spokesperson reportedly told Bernama.
“Although there is a reduction in its neutralising effect, Sinovac’s currentvaccine (CoronaVac) remains effective against the Delta variant."
It should be noted that lower vaccine effectiveness and highercontagiousness are both factors that will increase the number of people whoneed to be vaccinated to achieve herd immunity against the disease, thoughvaccines will still provide protection to the vaccinated individual.
Is it time for a third vaccine shot?
That depends on who you ask. Most experts would agree that the longer thispandemic drags on, the more likely a booster will become necessary to bolsterthe immune system. The question is: When?
Part of the problem - according to an explainer published in The Atlantic on June 24 - is that there is no consensus on what would constitute a worrying rise in breakthrough cases (i.e. Covid-19 infections despite full vaccination, especially if they cause symptoms) that would signal a need for booster shots to be administered.
"Instead, the experts are left to determine their own benchmarks for boosters, by evaluating the available information on antibody levels, breakthroughs, variant surveillance, and how different versions of the virus fare in labs and animal models, all while being mindful of the pandemic’s progress on scales both local and global.
“All of this intel then gets fed into a risk-benefit analysis, to determine whether the need for boosters outweighs any possible costs, which can span the medical to the economic,” the report said, quoting paediatrician Dr Grace Lee who advises the CDC on vaccine matters.
So far, Pfizer is the most outspoken on the need for an additional shot andhas already applied for US Food and DrugAdministration (FDA) authorisation to do so.
AstraZeneca and Sinovac are still exploring the need for boosters but havenot made any recommendations yet, though a group of Chilean researchers studying the Sinovac vaccine haverecommended a third dose.
There are also issues of vaccine inequity to consider – the WHO has spoken out against rich countries ordering boostershots at a time when some countries don’t even have enough vaccines to protecttheir healthcare workers.
Such considerations are not purely altruistic. There are concerns thatleaving large groups of people unvaccinated in any part of the world wouldcreate fertile ground for new variants to emerge and threaten the rest of theworld.
Ultimately, however, it is up to each country’s health authorities to decidewhether to approve additional doses, not pharmaceutical executives or smallgroups of researchers.
So far, the FDA has rebuffed Pfizer’s application anda closed-door meeting between Pfizer and US regulators on July 12 failed topersuade the regulators to change their minds.
Meanwhile, Israel has already startedadministering third Pfizer doses to those above 60 years old.
Thailand has started offering the Pfizervaccine as booster shots for its healthcare workers, while Indonesia is doing the same with the Moderna vaccine.Both countries’ healthcare workers are mostly fully vaccinated with the Sinovacvaccine.
Germany will be offering mRNA vaccines as booster shots either from Pfizer or Moderna to senior citizens and immunocompromised people starting next month, regardless of what vaccines they previously received.
In Malaysia, an expert panel under the Special Committee onEnsuring Access to Covid-19 Vaccine Supply will make recommendations on Friday regarding boostershots.
They will also make recommendations on whether those initially vaccinatedwith one vaccine can be given a different vaccine later.
This instalment of KiniGuide is compiled by KOH JUN LIN.