The Omicron variant has disrupted the return to normal in much of the world. With any new variant there are three questions which predict future potential impact.
- Is the variant more transmissible? Is it better at travelling from person to person.
- Does the variant escape existing immunity, whether natural or vaccine induced? This increases the number of people the variant can travel to.
- Does the variant cause more severe or more mild disease and how is this influenced by vaccination?
Understanding the potential threat from any new variant ultimately comes down to three key questions.
1. Is the new variant more infectious?
2. To what degree can the variant escape existing immunity (vaccine induced or natural)?
3. Does the new variant produce more mild or more severe disease?Data over the next few weeks will provide answers to the question about disease severity
We now have very good evidence that Omicron is widespread. Local epidemics are increasing rapidly. Data from South Africa, the UK and Denmark all show rapid growth with evidence of at least some degree of immune escape and reinfection. This suggests that the rapid growth is due to a combination of increased transmissibility and a greater ability to dodge existing immunity. All these locations have excellent testing capacity and high previous immunity from a combination of natural infections and vaccination. Data from the UK and Denmark suggests an epidemic doubling every 2 days. This suggests that a large wave of infections is on its way throughout the world. It is already trending larger than the Delta wave. We expect increasing talk internationally over the next few weeks around non-pharmacological interventions, such as social distancing regulations and mask mandates, in addition to increased roll out of booster vaccinations, in order to flatten the approaching wave. The early data suggests that two doses of a Covid vaccine are less effective at preventing transmission and mild disease against Omicron than other variants. They continue to give good protection against death and severe disease. This protection is significantly improved by booster doses.
It is important to appreciate that booster shots do not just restore the immunity which develops after the initial two shots. A booster shot has been shown to significantly improve both antibody response but also T cell and memory cell immunity. In some ways, there is an argument to say that the third shot is not technically a booster. Rather that the Covid vaccines require three shots for optimal immunity. More solid vaccination data will be available over the next couple of weeks.
The key question going forwards relates to disease severity. There have been a number of reports from South Africa suggesting that the disease associated with Omicron is milder. Whilst there are some reasons for cautious optimism, it is important to understand that South Africa is a very young population with high levels of natural immunity. The UK and Denmark also have high levels of immunity both natural and by vaccination. The impact of any variant would be expected to vary in different locations. We cannot necessarily assume that mild disease in highly immune populations would behave in the same way in immune naïve populations such as Hong Kong and China. It is also important to recognise that a large wave, of even very mild disease, can cause significant threats to a health system. A small percentage of a very large number may still be a large number over a short time. Even in South Africa the health system was under significant stress because of the numbers of healthcare workers who needed to isolate with mild infections.
What does this mean for Hong Kong?
In an article in July we argued that zero covid was not a long-term sustainable policy. One of the unintended consequences of a zero covid strategy without a plan for exit, is encouragement of rational vaccine hesitancy. Notwithstanding the controversies around quarantine and economic disruption associated with strict border control, the zero covid policies have been successful at keeping the disease out of our city. If the expected strategy was to continue for a protracted time without any disease there is really no incentive to get vaccinated at this point. We know from past experience that OT&P patients are generally accepting of Covid vaccines. More than 90% of our patients were vaccinated within the first two months of the government program. However, we have all, as doctors, had conversations with our patients who believe there to be no urgency for boosters or even primary vaccination in the context of no disease risk. In our opinion Omicron changes this dynamic. The likelihood of an accidental rather than planned transition increases with both the increase in transmissibility of Omicron and rapid rise in planetary viral load of the new variant. This significantly increases the risk of a virus getting into our city, however tight our border controls. In our opinion, the risk benefit has tilted in favour of early vaccination and we would advise OT&P patients to receive their booster doses as soon as they become eligible for them. Eligibility information is available here and online booking is available here.
In our Autumn newsletter we made the following statement:
‘The key is to develop the highest possible levels of vaccine-induced immunity, especially in the most vulnerable members of the population. This is by far the greatest challenge facing Hong Kong.’
This remains the case. Less than 20% of the over 80s are currently vaccinated. In a recent article we considered the arguments for and against vaccine mandates. There are philosophical and ethical arguments on both sides of this debate but regardless they are increasingly being introduced internationally.
We know that in addition to significantly reducing the incidence of death and serious disease, vaccination also significantly reduces the incidence and complications of Long Covid which in itself is likely to produce a significant burden on health systems in the coming years. We have collated some of the more interesting evolving evidence and research on Covid which we will keep up to date on our website. We also have a dedicated section collating research and patient information on Long Covid. For anyone who wishes to follow evolving Omicron data, we will share reputable sources of data here.
Finally, the potential increase in infective risk also impacts the risk benefit analysis around flu vaccination this year. Vaccination is advisable both to protect individuals but also to boost population immunity and avoid the potential impact of a combined flu and Covid epidemic. We have flu vaccinations available in all our clinics.
Wishing all our patients a Merry Xmas and a peaceful and healthy 2022.