(1/2) New study just out, face masks effective for source control against influenza and seasonal coronaviruses, even reducing virus detection in aerosols in patients with coronavirus infections. 5 years of hard work to generate the data
While it looks like Macau have got the current outbreak under control, after 13 rounds of universal testing, weeks of mobility restrictions, and more than a week of total lockdown, this was the first time in two years that such stringent measures have ...
(1/7) Worrying indications that the second wave of COVID-19 has now begun in Hong Kong, with more than 50 local infections being identified in the past few days and a large number expected to be reported later today.
Influenza disappeared from most of the world in the past 18 months, when influenza transmission was suppressed by the anti-COVID public health measures. But now influenza B is spreading again in mainland China and detections are increasing each week (1/9)
New preprint on Omicron severity just out. Key findings – intrinsic severity of Omicron is similar to ancestral Wuhan strain, but effective (observed) severity of Omicron is reduced in people who have been vaccinated and/or previously infected (1/16)
Latest news from Hong Kong (zero cases for 5 months now) - masks are mandatory in schools, and children are being asked to purchase special masks in order to attend instrument lessons . I thought it was a joke when I saw the picture. It's not a joke. Cost US$23, reusable.
(1/34) I saw this recent article in the BMJ, and I want to write a thread to explain (1) masks likely have a small to moderate effect on transmission, and (2) I don't believe the estimated 53% reduction here is a valid estimate of the mask effect
We're able to report our estimates of the effectiveness of COVID-19 vaccines, led by
@martinamc_m
with
@joshnealon
@gmleunghku
Both BNT and Sinovac vaccines provide good protection against severe Omicron BA.2; but elderly who received 2xSinovac need a 3rd dose of vaccine
(1/15)
This is fascinating because on-arrival quarantine is still set at 21 days, and the unnecessary 3rd week actually seems to have caused this particular community outbreak
Having been in the UK for a few weeks, I'm at Heathrow about to board BA31 back home to Hong Kong. I'll start a thread to document my experiences (1/x)
Short thread on
#COVID19
vaccines and vaccine hesitancy in Hong Kong. tl;dr summary: vaccines work, we should all choose to get vaccinated so that Hong Kong can get back to normal (1/17)
(1/9) Good news about COVID-19 suppression in Hong Kong, today we estimate that the daily reproductive number Rt dropped below 1 on 22 July, around a week ago
Hotel quarantine can *delay* the introduction of new strains into our community but it will not ultimately prevent their introduction. The 7-day quarantine policy has enormous economic costs to our city and very limited benefit.
⚠️🇭🇰🦠
BA.2.12.1 cases found in community. Suspected DQH transmission
Two travellers tested positive via Day 12 test at CTC.
Two other cases found in same hotel at same time of stay.
11 places (including restaurants) visited by the couple post DQH will be on CTN.
Our team have just collaborated with Guangdong CDC on a new preprint (not yet peer-reviewed) on the COVID outbreak in Guangzhou in May-June, and in this thread I’m going describe one of the findings relevant to quarantine durations (1/16)
(10/10) In combination, traveler quarantine, test+trace, face masks, and moderate physical distancing, all contributed to the successful suppression of
#COVID19
in Hong Kong without needing to resort to a lockdown.
I know of no scientific evidence to justify a 21-day quarantine period. 10 days with an exit test should be enough, 14 days more than enough. Anyone whose suspected exposure in Dorsett WC was only in the third week after their arrival was needlessly put at risk of infection...
@cqmrns_tg
Every week we seem to discover another downside to our ZeroCovid strategy, while one of the major advantages (quarantine-free travel with mainland) still hasn't materialised
I am very sad about the hamsters
(1/9) Good news about COVID-19 suppression in Hong Kong, today we estimate that the daily reproductive number Rt dropped below 1 on 22 July, around a week ago
(1/16) However, I don't follow the argument that the guidance has changed because of new evidence. The evidence has been there all along. I have a few comments on the most recent review in the Lancet
This is really great news! Masks can make a difference and should be recommended. Providing additional materials on when and how to wear masks is also very helpful.
I would like to know what scientific evidence is being used to justify the continued requirement that COVID vaccination uptake /must reach a specified level/ before it's safe for primary schools and secondary schools to operate for full days. I am not aware of such evidence.
@DrDOwens
Outdoor masking has minimal benefit, I agree with
@DrDOwens
that it adversely affects the credibility of health officials
I would recommend rescinding the outdoor mask mandate as soon as possible
Requiring masks to be worn during sporting activities will do more harm than good
Increasing the stringency of home isolation for cases in Hong Kong, with electronic tracking bracelets, will have a minimal effect on transmission. Scientific basis for my assessment is in the thread which follows … (1/27)
(7/7) When the second epidemic is controlled, this really emphasises the importance of keeping infections out through effective testing and quarantine of persons arriving in Hong Kong. Once an epidemic begins, it will take a lot of effort to stop.
(3/7) Clusters have been identified in an elderly home, a public housing estate, and linked with some restaurants. Test+trace has not prevented this. Mask-wearing in public is still universal, and has not prevented this.
(1/2) Fascinating article just out in Nat Microbiol. SARS-CoV-2 could be detected in samples collected in the ILI sentinel surveillance network in Wuhan from the first week of January 2020 onwards
If the epidemic situation is considered "severe", what is the marginal benefit of a hamster cull? There are still no documented hamster-to-human infections, and there could be better uses of resources for epidemic control? Just put a CTN on ppl who recently purchased hamsters ...
Maybe a silly question, but would these new measures have prevented any cases in the Moon Palace outbreak, if the measures had been in place for the last two weeks?
Starting January 7th, all major events will need to cancel.
Catering premises: After 6pm, no dine-in services. 6pm-4.59am. Maximum head count. 2 per table Cat B, 4 per table Cat C, 6 per table Cat D restaurants.
KTV, mahjong etc closed.
Bars/clubs closed.
Q: What happens with imported cases - still sent to hospital if confirmed? Any moves to reduce inbound quarantine to 7 days?
Dr Au: They still get sent to hospital. And no.
Hong Kong reduced on-arrival quarantine to 7 days starting April 1st, and there’s one post-quarantine test on Day 12
I suspect it won’t be too long before a positive is found on a Day 12 test, but *not* because of a long incubation period …
@tripperhead
@hkairport
Just over 2 hours for me
Process now much faster with RAT
I continue to recommend relaxation of all travel-related measures, since we know the current measures aren’t watertight and won’t be able to keep new variants out of HK. Enormous economic costs, minimal benefit.
I support daily RAT testing but not if the parents are expected to pay for it
Surely the govt should be paying for the tests for all children?!
I’m disappointed to see coercion of COVID vaccination in children, I think it’s inappropriate
Under Secretary for Education Dr Choi Yuk-lin:
• daily rapid testing shouldn't be too much of a burden for most families
• hopes schools can distribute RATs to families in need
• if fit enough to want to do ECAs, fit enough to get vaccinated
Regarding Hong Kong quarantine policy, unless writing the previous policy as "7+7", don't call the new policy "3+4"? It's not a change from 7 to 3+4, it's a change from 7+7 to 3+4, with the addition of amber code in the medical surveillance period. Hopefully next step 0+0!
Would be much more sensible to first reduce close contact quarantine to 10 days, doubling the effective capacity immediately
When was the last time a case was picked up in penny’s bay after the 10th day of quarantine?
Dr Chuang stated that the concept of home quarantine for close contacts is the absolute last possible option. Govt will attempt to find other quarantine centres.
A lockdown now for 2 weeks would save many more lives than a lockdown in late March that is implemented to facilitate contact tracing during mass testing cycles. More stringent social distancing now, for two weeks, would slow down transmission as we approach the peak, ... (1/3)
Sounds like case 12382 must have been infected in their third week of quarantine, because 12374 only arrived on the 4th November? Is this yet another example of the third week of quarantine doing more harm than good?
If there were a dangerous new variant somewhere in the world and HK wanted to /delay/ it’s spread in the Hong Kong community, flight suspensions with 3+ new-variant cases might make sense, but all the cases coming in are Omicron, of which we’ve got 1000+ infections per day …
Q (BBG): Almost 60 flight bans this year. Shortage of DQH rooms. Biz community not happy. Any plans to remedy this?
CL: Flight route suspension mechanism is staying. We're finding more rooms though.
New paper with
@weywenlim
and
@sarahcobey
- could fractionation solve the global shortage of
#COVID19
vaccines? tl;dr we could consider reducing the dose of individual vaccines so that more people could receive at least some protection, more quickly (1/20)
We are going to pause the daily updates of Rt on our HKU COVID dashboard now that there are no recent local cases, and fingers crossed it will stay that way for a while!
(1/10) Recent situation in hospitals in HK is very concerning. Following tweet includes information complied from daily press releases each of which refer to the preceding 24h (I excluded info on the approx 2000 mild cases isolated in Penny's Bay) ...
Omicron is a greater threat to health systems than to individuals
Health systems in ROW almost crashed by illness/isolation in HCW’s
If health systems crash all cause mortality at all ages increases. People die of covid/heart disease/ asthma etc
1/5
I recommend children to get COVID-19 vaccination, but I don't think there's sufficient justification to *require* children to get vaccinated, and I'll explain my reasoning ... (1/15)
The
#HongKong
government has announced that schools are required to have all of their staff members and at least 90 percent of students double-jabbed against
#COVID19
in order to resume full-day in-person classes
For COVID-19, contact tracing works by identifying people who have been exposed to known cases typically based on prolonged close contact. It looks like contact tracing won't work as well against Omicron in HK -- transmission appears to be occurring without close contact? 1/4
Brief thread on containment vs mitigation. Summary point - I hope there's a plan for intense mitigation measures in China in the next 1-2 months, as part of the transition to living-with-COVID
(1/9)
(34/34) Due to the flaws in the underlying studies, I don’t believe that the 53% risk reduction is a valid estimate of the real-world effectiveness of face masks. There’s good evidence that they work, I’m just not convinced by this specific estimate of their effectiveness
Hong Kong update - exponential rise in BA.4 and/or BA.5 (probably BA.5) continues. BA.2 cases now stable and will probably be declining soon, looks like we've hit herd immunity to this subvariant for now ... (1/6)
(2/7) Our estimate of the effective reproductive number "Rt" for local infections is close to 3, which is concerning It will take a lot of effort to bring down such a high reproductive number.
@egyptiankinghk
@xennialmatt
@tripperhead
Getting back to zero daily cases within the next few weeks is impossible
It might not be impossible to get back to zero daily cases in perhaps 4 months from now, when potentially most of the population will be immune
When I think about the public health rationale for the ZeroCovid strategy in the era of effective vaccines and effective treatments, I do sometimes wonder whether the same rationale would also support a ZeroInfluenza strategy and oppose "living with influenza"? (9/9)
(5/7) Implementing work-from-home for civil servants and private businesses, closing bars and leisure facilities, and enhancing social distancing in restaurants was able to bring the first wave under control, and hopefully similar measures will be able to halt this second wave.
Hong Kong taxpayers are paying tens or even hundreds of millions of HK$ per month so we can tell other countries what strains are prevalent in their countries, and have a weeks advanced notice of what’s likely to be spreading in HK (which we can guess anyway)
BA.5: 89.3%
BA.4: 4.9%
BA.2.12.1: 1.3%
29 XBB cases found in imported cases, 24 positive on arrival, five found on Day 2 testing. 44.8% came from Singapore
@JShijiu
@tripperhead
ZeroCovid was a good strategy prior to the availability of vaccines, but has limited rationale after vaccines are widely available, and in my opinion it increases hesitancy in elderly (they may think the govt will protect them from getting COVID)
(6/7) How did the second wave start? We may never know, but given the absence of local cases for most of the past 3 months, these latest outbreaks may have been started by relatively more recent importations.
🚨
Head of the Communicable Disease Branch of the Centre for Health Protection of the Department of Health, Dr Chuang Shuk-kwan:
For close contacts from case
#12924
onwards, quarantine will be 14 days in a quarantine centre, followed by 7 days home isolation. Test on Day 19.
Thread. Preliminary analysis of immune responses following receipt of BNT/Fosun and Sinovac vaccines with
@weywenlim
and
@gmleunghku
now published in Lancet Microbe. tl;dr we find substantial differences in antibody levels between the two vaccines (1/16)
My article with Theo Chan published today in Mingpao (in Chinese) argues that while COVID vaccines should be *recommended* for younger adults in HK, we believe there is insufficient justification at present to *mandate* vaccination in this group … (1/24)
In August 2021 we reported compelling evidence that quarantine for Delta can safely be shortened from 21 days to 10 days
Omicron latent period is likely even shorter than Delta latent period
In January 2022, 5 months later, HK finally shortens quarantine from 21 days to 14 days
While there's been discussion about the incubation period in terms of quarantine duration, what we really need to know is the /latent period/. Our results indicate that a 10-day on-arrival quarantine for vaccinated persons can minimise the risk of Delta introductions (16/16)
Really difficult to see the rationale for a mask mandate at this point
Mandate only justified if (1) high masking rate is essential for protecting public health plus (2) masking rate will be low without a mandate.
Secretary for Health, Professor Lo Chung-mau:
I can't stress enough the importance of face masks. Even if the mask mandates is dropped, I'm sure many of the public will continue to wear them.
Thread on our new preprint (not yet peer reviewed) on the low but non-zero risk of COVID-19 transmission in quarantine hotels in Hong Kong, with
@dcadam
@gmleung
@worldepidemic
and other colleagues (1/32)
From the SCMP article earlier today, I was surprised at the prediction of 10,000 patients needing hospitalization. The level of peak incidence would have to be very high to result in 10,000 patients needing hospitalization, now that we have high vaccine coverage and some ...(1/4)
I think this is very wishful thinking
Look at the near-vertical epidemic curves of Omicron in most other countries. Omicron is _much_ more transmissible than previous strains
Test and trace won't break every transmission chain, even when done as well as it's done in Hong Kong
(4/7) In our analysis of the first wave, we estimated that Rt rose above 2 in late March. This occurred even though we were doing a lot of testing and contact tracing, everyone was wearing face masks, schools were closed, and mass gatherings discouraged.
(7/10) Almost everybody in Hong Kong was wearing masks in public throughout the epidemic. But there was evidence of community spread in early March, despite this universal masking and test+trace.
@tripperhead
If we were only using BioNTech or other highly effective vaccines, and not using Sinovac, it would be easier to propose dropping quarantine for fully vaccinated persons
Thread on “sustainable endemicity” versus “ZeroCovid” as alternatives for Hong Kong. Key point, if aiming for “sustainable endemicity”, extending quarantines should only be a short-term measure. Tighter domestic and border measures would be needed to sustain ZeroCovid (1/21)
@Birdyword
@tripperhead
There is no flu "season" in Hong Kong, we can have influenza epidemics at any time of the year. Flu is winter-seasonal in temperate climates, but doesn't tend to have strong/predictable seasonality in subtropical areas like HK
Fantastic opening to our 3-day international conference this morning
#immunity2023
with many excellent presentations including opening talks by Malik Peiris and Maria Van Kerkove
(6/10) In our other preprint on superspreading we reported just one example of a 'failure' of quarantine – a close contact was quarantined without symptoms but had already passed on infection to his wife (footnote 1 in Figure 3 of that preprint)
Fascinating article well worth a read: "The unintended consequences of COVID-19 vaccine policy: why mandates, passports and restrictions may cause more harm than good" by an international group of authors in BMJ Global Health
Influenza is not strongly winter-seasonal in Hong Kong. We have had large summer flu seasons before.
Indoor mask mandate should only be a measure of last resort during a v large epidemic, if voluntary mask use low. Shouldn't be a permanent rule. Outdoor mask mandate has no basis
Government advisor Professor Ivan Hung says he expects the government to relax outdoor mask mandates by next summer.
This is the same Professor Ivan Hung who said he expected the government to relax mask mandates by last summer.
THREAD .. It's so difficult trying to keep up with changes in case definitions. Based on the experience with SARS, two classifications helped greatly: "suspected case" and "probable case"
(7/10) Almost everybody in Hong Kong was wearing masks in public throughout the epidemic. But there was evidence of community spread in early March, despite this universal masking and test+trace.
My op-ed in Mingpao explains the likely threshold for herd immunity is high because
#COVID19
is so easily spread. It is unlikely that we could reach herd immunity unless we vaccinate at least 2/3 of the population with highly effective vaccines. (1/10)
(8/10) Community measures were important in suppressing transmission. Work-at-home was implemented for civil servants and many private businesses in February, stopped in March, and re-implemented later in March. We estimated this reduced transmission by 67% when in place.
With an exponential increase in infections indicated by the trend in unlinked cases, it would be reasonable to expect a large jump in cases when testing picks up after the Lunar New Year (1/14)