Independent report

Suspension of the 15-minute wait for vaccination with mRNA vaccine for COVID-19: UK CMOs' opinion

Published 14 December 2021

The Chief Medical Officers (CMOs) of the UK and lead Deputy Chief Medical Officers (DCMOs) for vaccines have considered whether, in the light of the very considerable need to speed up vaccination and boosting in response to Omicron variant, the 15-minute wait for some mRNA COVID-19 vaccines should be suspended.

Their view, having considered the views of the COVID-19 Vaccine Benefit-Risk Expert Working Group (EWG), NHS planners and others is that with the low rates of anaphylaxis, in the context of the considerable need for people to be boosted or vaccinated, the 15-minute wait after a vaccination with mRNA vaccine will cause more harm than it can avert because it will significantly reduce the number of people who can be vaccinated over a short period of time. The 15-minute wait should therefore be suspended for first, second and homologous or heterologous boost vaccinations with mRNA vaccine given the current situation, with this operationalised in line with the needs in each of the 4 nations.

The long-term decisions on the 15-minute wait, when the current need for extreme speed of vaccination and boosting is over, should rest with the Commission on Human Medicines (CHM), the Medicines and Healthcare products Regulatory Agency (MHRA) and the Joint Committee on Vaccination and Immunisation (JCVI). If Ministers agree then this should be a temporary measure on the grounds of public health need to protect as many citizens as possible over a short period of time. How the 15-minute suspension is operationally implemented should be determined by each nation.

The CMOs recognise that this will lead to a marginal increase in risk for a very small number of people, but substantially fewer than would be harmed by a slower vaccine rollout in the current public health emergency leading to some citizens not getting boosted or vaccinated prior to exposure to Omicron. This includes a consideration that any prior vaccination and particularly boosting is likely to lessen the likelihood of severe disease arising from Omicron variant infection.

Those with a history of allergic reactions should be managed in line with Green Book advice and everyone who is vaccinated should be given verbal and written advice on allergic reactions including what actions to take if they become unwell.

The background to this decision is laid out below.

We will copy this to the Chair of CHM and JCVI for information.

Background

The current threat and response

Omicron is spreading extremely rapidly, with a doubling time of 2 to 3 days. If this is maintained, it will spread extremely rapidly through the population. Even if less severe than Delta, with the very high numbers involved modelling from several groups show this will cause substantial mortality, severe illness and pressure on the NHS. This constitutes a national health emergency.

While some protection by any level of vaccination against severe disease is likely, data to date show that 2 doses of any available vaccine is not sufficient to prevent symptomatic disease.

There is therefore a need to boost as much of the population as possible before the peak of the Omicron wave, or provide first vaccination to those with no prior protection. It is likely that this will significantly reduce the number of people becoming ill, hospitalised and dying. Given the speed of the current wave this will need to be undertaken very rapidly.

The mRNA vaccines have shown better ability to boost and are therefore the basis for the current booster campaign. In the CovBoost study antibody responses to mRNA vaccine boost were also much quicker than for other vaccine modalities (typically 7 to 10 days).

Basis of the 15-minute wait

All currently deployed vaccines have proven safe with low rates of severe side effects. As with all vaccines occasional cases of anaphylaxis have been reported, and the rates are slightly higher (but still very low) in the case of mRNA vaccines from Pfizer/BioNTech and Moderna but still overall very rare. For mRNA vaccines there have been 2 fatal Yellow Card reports of anaphylaxis linked to primary course vaccination and no deaths from anaphylaxis linked to booster vaccination reported in the UK to date.

We extract below some of the key points from the COVID-19 vaccine benefit-risk expert working group (EWG) analysis on booster vaccination:

a) Anaphylaxis following mRNA COVID-19 vaccination is a very rare but a potentially life-threatening event.

b) The EWG has previously stated that occurrence of anaphylaxis, where the first 2 doses of the same vaccine have been previously administered with no allergic reaction, would be extremely unlikely and agreed that the 15-minute observation time can be waived for homologous boosters (where the booster is the same vaccine as the first 2 doses) where no allergic reaction occurred on the first 2 doses.

c) The overall reporting rate of anaphylaxis with booster doses (0.26 per 100,000) was below that of reporting for the first 2 doses, with Moderna (1.47 per 100,000) and Pfizer (1.23 per 100,000). There had been 28 reports of anaphylaxis events with Pfizer booster doses (12 on a homologous i.e. Pfizer boosters, after Pfizer first/second dose; and 16 on heterologous schedule (i.e. Pfizer booster after AZ or Moderna or where primary dose was unspecified first and second doses).

d) Five of the 28 anaphylaxis Pfizer reports met the case definition criteria for anaphylaxis; of which 4 were heterologous, the fifth case was homologous, but the patient had received concurrent flu vaccine which is a potential co-suspect in the case. There were 9 reports of anaphylaxis events with Moderna booster doses, all reports on a heterologous schedule.

e) Within the 15-minute waiting time 17 events were reported and outside the 15-minute waiting time, 14 events were reported, but within the same day. The exact timings were not always specified, for instance – several said’<1 day’ or ‘after a few minutes’ or ‘outside the vaccination centre’. Six reports indicated an onset time of 5 minutes or less from vaccination.

f) There were no fatal reports, however 18 of the reports stated adrenaline was administered and 8 were hospitalised. It was noted that several had pre-existing allergies to a variety of allergens.

Reports with the Yellow Card database are under constant review and subject to change. This can include of receipt of additional information on reports, including additional reactions or details which may lead to identification of duplicated information. As such numbers of events may fluctuate.

The CMOs take these data as read. They demonstrate a real, but very rare, absolute risk with 2 reports of fatalities. It is not clear whether the 15-minute wait contributed to the non-fatal outcomes. The 15-minute wait was observed in the reports with fatal outcomes.

The risks of the 15-minute wait in the current situation

Initial analysis from NHS England from England, which is likely to be similar to other nations, implies that under the conditions of a system working at full capacity (as is needed now) the 15-minute wait reduces throughput by 23%. This leads to over 500,000 people not getting a vaccine in the initial period who would otherwise have done so.

Even allowing for the relatively crude initial calculations here, the absolute number of people put at risk because they cannot get vaccinated due to the 15-minute wait (in the high tens of thousands or higher) is much greater than the more precisely calculated number who get anaphylaxis.

Since the mortality rate for COVID-19 is non-trivial (although not yet calculated for Omicron) the probability of harm through delay is, in the view of the CMOs substantially in excess of the probability of benefit from maintaining 15-minute waits under the current situation.

The CHM has also agreed that the 15-minute observation period for primary course, third doses and booster doses of mRNA vaccines could be waived on a temporary basis during the emergency response to the Omicron variant. They will keep this under close review.

CMO for England, Professor Chris Whitty

CMO for Northern Ireland, Professor Sir Michael McBride

CMO for Scotland, Professor Gregor Smith

CMO for Wales, Dr Frank Atherton

DCMO lead for vaccination (England), Professor Jonathan Van Tam

DCMO lead for vaccination (Northern Ireland), Dr Naresh Chada

DCMO lead for vaccination (Scotland), Professor Nicola Steedman

DCMO lead for vaccination (Wales), Professor Gillian Richardson