By Ben Cowling and Theo Chan

Stage three of the Vaccine Pass will start in Hong Kong on May 31, by which time all applicable individuals aged 12 or above (except those with a documented infection and in certain special groups) will need to have received at least two doses of Covid-19 vaccines and have received the third dose six months after their second dose. 

When vaccine passes are needed for essential activities such as access to educational institutions and workplaces – making it almost impossible for young adults to refuse vaccination – they essentially function as a vaccine mandate.

Patrons must present their vaccine or exemption QR code upon entry at most premises under Hong Kong’s Vaccine Pass scheme. File Photo: HK Gov screenshot.

Here we review the relevant ethical considerations, assess the situation in Hong Kong, and explain why we believe there is – at present – insufficient justification to restrict the movements and activities of young adults who do not satisfy the vaccine pass criteria.

Vaccine passes have been used in various parts of the world in the past year to increase vaccination uptake, recognising that high vaccine uptake will reduce the health impact of Covid epidemic waves. According to the World Health Organization, mandating vaccination or any other medical procedure requires strong justification such as an emergency situation.

Since the implementation of the vaccine pass policy in February, the situation in Hong Kong has been rapidly changing and we should review the policy from time to time. 

Principle of informed consent

Informed Consent” is an important principle in medical laws and ethics which applies to most medical procedures, including the administration of vaccines. Under this principle, it is important that a mentally competent person undergoing the procedure understands what is involved, and specifically is aware of the risks and benefits.

A well-informed patient is fully entitled to exercise the right to refuse treatment, even if it offers them more benefits than risks. In other words, even though there are substantial health benefits of vaccination for an individual, the right to refuse vaccination, in general, should be respected. 

A Covid-19 vaccination centre in Hong Kong. Photo: GovHK.

However, when facing a public health emergency, relevant public health law and ethics principles allow the restriction of individual autonomy to attain greater societal good, but such restriction should be necessary, reasonable,  proportionate, and kept to a minimum.

With reference to vaccine passes, there would only be sufficient grounds to restrict the rights of unvaccinated young adults – or even forbidding them from going to school or work – if their refusal collectively puts public interests at very great risk of harm, for example, by risking the collapse of the public health care system. 

Herd immunity and dynamic zero-Covid

Hong Kong currently adopts a dynamic zero-Covid strategy, the aim of which is to minimise the number of infections and ideally to keep daily local infections at zero for long periods of time. In Hong Kong, control of Covid has been achieved through restrictive public health measures, such as international travel restrictions and social distancing measures in the community.

Since February 2021, Covid vaccines have been made available to the public. Currently, with vaccines available to everyone aged 3 and above, 92 per cent of our population have received one dose of vaccination and 86 per cent have received two doses.

Photo: GovHK.

At the start of the vaccination campaign, there was a lot of discussion about the idea that vaccinating a high percentage of the population could build population immunity against infection to a high level, thereby reducing the potential for the spread of the disease in the community, as well as indirectly protecting those who cannot receive vaccination.

However, we now recognise that Covid vaccines provide only limited protection against infection with circulating variant strains which differ from the strain included in the vaccine, although current vaccines do continue to provide a high level of protection against severe disease with variants. 

We at the HKU School of Public Health estimate that more than 4 million Hongkongers have been infected by Omicron BA.2 in our fifth wave despite our high overall vaccine coverage just prior to and at the beginning of the fifth wave. Despite the limited efficacy of the current vaccines to prevent infection with variant strains, the high level of population immunity attained from the high vaccine coverage combined with the high cumulative incidence of infections has brought the fifth wave to an end in recent weeks.

While BA.2 may resurge after social distancing measures are relaxed, and new subvariants and variants will likely spread in our community in the future, the level of vaccine coverage would not make much difference to the future level of transmission in the community because current vaccines have a limited effect on transmission. 

Preventing collapse of public health system

Covid poses very different risks to older people and young adults. During a Covid epidemic, it’s crucial that the public health care system is protected so its services are available to these individuals who need medical care.

Both Covid vaccines available in Hong Kong provide a high level of protection against severe Covid. Covid can be severe in all ages. However, almost all severe cases and deaths in Hong Kong have occurred in unvaccinated elderly. Only 4 per cent of the Covid deaths in Hong Kong’s fifth wave occurred in those under 60 years of age.

There are two reasons for the much lower rates of severe cases and deaths in young adults compared to older adults in Hong Kong. First, for unvaccinated persons below the age of 60 the risk of severe Covid is intrinsically lower, compared to older individuals. Second, a very high vaccine coverage in younger people has already been achieved, as the coverage exceeds 90 per cent with at least two doses, and with this high coverage they are now at even lower risk of severe infection and death. 

Caritas Medical Centre in Sham Shui Po, Hong Kong during Hong Kong’s fifth wave of Covid-19. File Photo: Kyle Lam/HKFP.

For adults aged 18 to 59, a third dose of Covid vaccination can certainly boost protection against severe disease from a very high level to an even higher level. Compared to two doses of CoronaVac, which provide 92 per cent protection, and two doses of BioNTech, which provide 95 per cent protection against severe disease, a third dose of either vaccine increases protection to above 98 per cent. 

Because of the high vaccination coverage and high level of natural immunity acquired after the fifth wave of infections, and the lower rate of severe disease in young adults anyway, it would be expected there would be very few severe cases in young adults in a future epidemic.

Even if some remaining unvaccinated young adults now refuse to receive vaccination, or those who received only one or two doses now decline to receive a third dose, locally their overall risk of getting severe disease is still low.

Focus on protecting high-risk older adults

Currently, vaccine uptake remains relatively lower in older adults. Among those aged 70 to 79, more than 78 per cent have now received two vaccine doses and 42 per cent have received a third dose. Among those aged 80 or older, just over 50 per cent have received two doses but only 17 per cent have received a third dose.

A variety of reasons have led to high hesitancy to receive COVID vaccination in this group. We hope such hesitancy would abate now in view of 9,000 deaths in the fifth wave. 

Elderly people queue up for vaccination. File Photo: GovHK.

Although the fifth wave is almost over, Hong Kong will have further waves sooner or later, and, as before, older adults will likely face the highest risk of severe disease and death in subsequent waves.

Increasing vaccination coverage in older adults including booster doses will continue to be a priority. Vaccine passes in older adults may be justified if vaccine coverage in this group remains low and cannot be achieved by other approaches.

Relaxations for younger adults

The doctrine of informed consent allows a person to refuse any vaccination. The core justification for applying a vaccine mandate that supersedes this principle and restricts individual freedom should be that it is necessary in order to protect the collective interests of the community.

There should be a very compelling case and strong scientific justification when a citizen is in essence prevented from studying or going to work without undergoing a particular medical procedure such as vaccination. 

In Hong Kong, we already have a high coverage of two vaccine doses in young adults and many people infected in our fifth wave already benefit from post-infection immunity. While we recommend all eligible Hong Kong citizens – especially older adults – to receive three or four doses of vaccines as appropriate, we do not think there is any strong justification to mandate additional doses in young adults to push uptake beyond the level of uptake that could be achieved without coercion.

Thus, we would advocate for a relaxation of the policy of vaccine passes for non-elderly groups in Hong Kong. 

Ben Cowling is Chair Professor of Epidemiology at the School of Public Health at HKU. Theo Chan is Honorary Assistant Professor in the Department of Pharmacology and Pharmacy at HKU.

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