19th April 2021 – (Hong Kong) The COVID-19 Vaccination Programme has been implemented for the 53rd day since 26th February, 2021 and so far, about 1,091,100 doses of COVID-19 vaccines have been administered for members of the public. About 371,200 persons have received their second dose, with about 223,100 persons receiving the Sinovac vaccine and about 148,100 persons receiving the BioNTech vaccine.

From 23rd April onwards, COVID-19 vaccination will be made available to 1.08 million Hongkongers who are aged between 16-29. The age group of the whole vaccine programme covers about 6.5 million people, accounting for about 88% of the total population of Hong Kong. Assuming that the government only needs to vaccinate the bare minimum of 70% of the 6.5 million population i.e. 4.55 million, it will take almost 3 years for the 70% population to complete the second dose of vaccination. Moreover, the protection rate for even the most potent vaccine at present day i.e. BioNTech can only last for 6 – 9 months.

To make matter worse, the coronavirus variant discovered in South Africa may evade the protection provided by Pfizer/BioNTech’s COVID-19 vaccine to some extent, a real-world data study in Israel found, though its prevalence in the country is very low and the research has not been peer reviewed. The study, released on Saturday, compared almost 400 people who had tested positive for COVID-19, 14 days or more after they received one or two doses of the vaccine, against the same number of unvaccinated patients with the disease.

Also, the latest variant discovered in India and 77 cases of which have also been found in U.K. will make herd immunity a tall tale to achieve.  The B.1.617 variant includes a number of mutations. The Indian Health Ministry has said that such mutations increase infectivity and aids in escaping immune response.  None of the vaccines have been tested on the new Indian variant so far.

Recently, a N501Y variant has entered the Hong Kong community through an Indian engineer who came to Hong Kong from Dubai.

According to a feature article published in NATURE, as COVID-19 vaccination rates pick up around the world, people have reasonably begun to ask: how much longer will this pandemic last? It’s an issue surrounded with uncertainties. But the once-popular idea that enough people will eventually gain immunity to SARS-CoV-2 to block most transmission — a ‘herd-immunity threshold’ — is starting to look unlikely.  In February, independent data scientist Youyang Gu changed the name of his popular COVID-19 forecasting model from ‘Path to Herd Immunity’ to ‘Path to Normality’. He said that reaching a herd-immunity threshold was looking unlikely because of factors such as vaccine hesitancy, the emergence of new variants and the delayed arrival of vaccinations for children.

Long-term prospects for the pandemic probably include COVID-19 becoming an endemic disease, much like influenza. But in the near term, scientists are contemplating a new normal that does not include herd immunity. Here are some of the reasons behind this mindset, and what they mean for the next year of the pandemic. The COVID-19 vaccines developed by Moderna and Pfizer–BioNTech, for example, are extremely effective at preventing symptomatic disease, but it is still unclear whether they protect people from becoming infected, or from spreading the virus to others. That poses a problem for herd immunity. “Herd immunity is only relevant if we have a transmission-blocking vaccine. If we don’t, then the only way to get herd immunity in the population is to give everyone the vaccine,” says Shweta Bansal, a mathematical biologist at Georgetown University in Washington DC.  Also, the speed and distribution of vaccine roll-outs matters for various reasons, says Matt Ferrari, an epidemiologist at Pennsylvania State University’s Center for Infectious Disease Dynamics in University Park.

Even as vaccine roll-out plans face distribution and allocation hurdles, new variants of SARS-CoV-2 are sprouting up that might be more transmissible and resistant to vaccines. “We’re in a race with the new variants,” says Sara Del Valle, a mathematical and computational epidemiologist at Los Alamos National Laboratory in New Mexico. 

Calculations for herd immunity consider two sources of individual immunity — vaccines and natural infection. People who have been infected with SARS-CoV-2 seem to develop some immunity to the virus, but how long that lasts remains a question/ Given what’s known about other coronaviruses and the preliminary evidence for SARS-CoV-2, it seems that infection-associated immunity wanes over time, so that needs to be factored into calculations. Modellers won’t be able to count everybody who’s been infected when calculating how close a population has come to the herd-immunity threshold. And they’ll have to account for the fact that the vaccines are not 100% effective. If infection-based immunity lasts only for something like months, that provides a tight deadline for delivering vaccines. It will also be important to understand how long vaccine-based immunity lasts, and whether boosters are necessary over time. For both these reasons, COVID-19 could become like the flu.

At current vaccination rates, Israel is closing in on the theoretical herd-immunity threshold, Aran says. The problem is that, as more people are vaccinated, they will increase their interactions, and that changes the herd-immunity equation, which relies in part on how many people are being exposed to the virus. “The vaccine is not bulletproof,” he says. Imagine that a vaccine offers 90% protection: “If before the vaccine you met at most one person, and now with vaccines you meet ten people, you’re back to square one.”

Ending transmission of the virus is one way to return to normal. But another could be preventing severe disease and death, says Stefan Flasche, a vaccine epidemiologist at the London School of Hygiene & Tropical Medicine. Given what is known about COVID-19 so far, “reaching herd immunity through vaccines alone is going to be rather unlikely”, he says. It’s time for more realistic expectations. The vaccine is “an absolutely astonishing development”, but it’s unlikely to completely halt the spread, so we need to think of how we can live with the virus, Flasche says. This isn’t as grim as it might sound. Even without herd immunity, the ability to vaccinate vulnerable people seems to be reducing hospitalisations and deaths from COVID-19. The disease might not disappear any time soon, but its prominence is likely to wane.

Part of this article appears on NATURE.com.

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