Thread by @GKangInd

So many calls about China, about what that means for India, about XBB, about 3rd waves, about new mandates, about travel bans, about vaccine boosters- thought best to get views out to summarise the current situation. Long thread, be warned 🙂 1/n

Let's start with China. China is opening up fast at a time when their population has low levels of exposure to natural infection. The current circulating variants are Omicron, which have evolved in vaccinated populations and are therefore very infectious. 2/n

This means that China will have lots & lots of infections. Remember India's 100s or 1000s of cases in April-May 2021 and Jan 2022? In the absence of significant mitigations, this will be similar. Lots of infections lead to lots of sick people. 3/n

Most of China's population has received 2 doses of vaccines. Most infections can be managed at home, but sheer numbers mean that even a small proportion getting severely ill, means that many people will have severe disease and that a proportion of those will die. 4/n

The risk factors for severity remain the same. Older age (& news from funeral homes in China indicate that the age related mortality pattern has not changed) & co-morbidities will continue to be drivers of severe disease & deaths. Lots being said about 'ineffective' vaccines. 5/n

Most of China has received 2 doses of inactivated vaccines with low levels of boosting (although the government is trying to boost boosters). AFAIK, the Sinopharm vaccine has been used mainly in China, but good data from the similar Sinovac/Coronavac vaccine from Lat Am. 6/n

The Chinese inactivated vaccines work well to prevent severe disease/death, but somewhat less well than the mRNA/vectored vaccines. A booster with these will help, but other platforms likely to be better. Hope we get effectiveness data from China, but probability low. 7/n

So the vaccines will prevent a proportion of severe disease/deaths, but numbers of people needing hospitals and dying will be higher than we have become used to in the past several months. BUT this will be higher than with slower opening or at a different time, 2 reasons. 8/n

When lots get sick, that includes healthcare workers. Understaffed, overloaded hospitals mean poorer care for patients. Also in winter, other viruses/infections result in more hospitalisations (the tripledemic in the rest of the world), making this bad time in hospitals.9/n

Chinese govt pushing vaccinations, getting Paxlovid all good but with peak travel time coming up, this is a race against time. China may have to experience in weeks what the rest of the world saw over years. 10/n

What does this mean for the rest of the world? New variants? Why not travel bans? What should we be doing? 11/n

As far as we know, there are no new variants. China has the capacity to sequence, & we hope it will share data in real time. The variants now circulating in China have been in the rest of the world for months. The behaviour of the virus is not any different from expected. 12/n

In India as well, we already have XBB and BF.7 (the 2 being hyped as new monsters). They are, like all Omicron subvariants, very good at infecting people because they escape the immune response that prevents infection, but are not causing more severe disease than delta. 13/n

Omicron does result in severe disease in a proportion of infected, but not as severe as delta. It is not mild, but it does infect the upper respiratory tract more than lower. Each new subvariant thrives only if it is better at immune escape than the prior ones. 14/n

Therefore, greater infectiousness of new variants is a given & not news. Worry with China is not just the tragedy unfolding for them as they undergo what we have already experienced, but that high levels of replication mean increased opportunity for new variants to emerge. 15/n

For this, they & we should maintain variant & clinical surveillance to ensure that we detect signal of any changes in the behaviour of the virus. This is a public health function where stable surveillance runs in the background & ramps up for emerging threats. 16/n

What should stable surveillance be? All cause severe acute respiratory infection surveillance at all or sentinel hospitals (depending on resources), detection & investigation of clusters. Periodic serosurveys & environmental surveillance can be useful depending on pathogen. 17/n

Randomly increasing testing has little value. Testing incoming travellers needs a risk based framework, but X% sampling also means that you accept that every incoming case will not be detected. In other words, increasing testing needs a strategic approach. 18/n

Does all of the hype mean that the threat to India is high? Our population is vaccinated with the primary series, & has had high rates of infection (90% estimated). Most infections were during Omicron, & this gives us hybrid immunity. How long will it last & vaccines? 19/n

At the moment, India is doing fine. We have few cases, we have had the XBB & BF.7 for a while and they have not driven an upsurge in India. In the absence of an even more highly infectious variant, I do not expect a surge. 20/n

But will we be able to detect a new variant or a surge? We have ample sequencing capacity & if sequencing is done in real-time, absolutely we can. When hospitals begin to see severe cases, we will know. Need to & can understand & measure both the virus & the disease. 21/n

A signal maintained over a couple of weeks is a generally useful construct of the shape of the future. Look at where we are in India. There is no signal at the moment, & we are watchful. 22/n

So to vaccines. Who needs boosters? Booster doses on any platform are likely to have an incremental benefit in anyone, at least for a while. Among vaccines in India, all vaccines fine, but order based on immune response will be protein, adenovirus vectored, inactivated. 23/n

Two doses of any vaccine protect against severe disease/deaths. We have no data from India 😔that any Indian vaccine has a reduction in effectiveness over time, but from the rest of the world, the value of a booster in the elderly population is clear. 24/n

So if you have an elderly person in your family, please get them an additional dose, as a precautionary measure even without any Indian data. May help, unlikely to harm. 25/n

For younger. healthier people, the value is likely to be less, but not zero. For public health programmes to be delivered by government, this is a different situation where vaccinating everyone for marginal benefits means that other healthcare will be deprived of resources, 26/n

So without data & comparative analysis, I am unsure what the need & potential impact a booster vaccination for all will have as a public health programme. But the need for continued surveillance, I am sure about. 27/n

Now to other interventions. Masks? I think more important than mandate is an understanding of the purpose & setting for mask use. 28/n

If you have any respiratory infection, stay home. If you need to go out, go masked. If you are vulnerable, stay masked in unfamiliar company or if someone around you is obviously ill. If there is a lot of infections/cases in the community, staying masked in crowds is good. 29/n

If you are healthy & there is little infection in the community, outdoors, how much value does masking have? (And really the best masks--not cloth, not the used for 5 days tatty masks). That depends on your individual risk perception, but to me, very little. 30/n

Next FAQ is- should we travel? Risk perception again, but no need to stop right now. There is very little infection in India. Travel, wear a mask if you are worried. Outside India, some places have more infections, wear a mask & go travel (not China at the moment). 31/n