Coronavirus (COVID-19): state of the epidemic - 13 May 2022

Resilience: Vaccine Uptake, Antibody Estimates, and Vaccine Effectiveness

Vaccine Uptake

Vaccinations started in Scotland on 8 December 2020 and there has been a very high uptake. Covid-19 vaccines protect most people against severe outcomes of a Covid-19 infection, but some people will still get sick because no vaccine is 100% effective. The current evidence suggests that you may test positive for Covid-19 or be reinfected even if you are vaccinated, especially since the emergence of the Omicron variant in the UK. The major benefit of vaccination against Omicron is to protect from severe disease. More information is available on the PHS website.

By 9 May, almost 4.4 million people had received their first dose, an estimated 90.3% of the population in Scotland aged 12 and older. Over 4.1 million people had received their second dose, an estimated 85.9% of the population aged 12 and older. Additionally, almost 3.5 million people in Scotland had received a third vaccine dose, which is an estimated 72.8% of the population aged 12 and older^[53].

The JCVI now advise a spring booster dose of the Covid-19 vaccine for: adults aged 75 years and over, residents in care homes for older adults, and individuals aged 12 years and over who have a weakened immune system^[54]. By 9 May, 426,678 fourth dose vaccinations had been administered, with 75.7% of all care home residents having received their fourth dose. It is also estimated that 75.2% of those aged 75 or older have received their fourth dose^[55].

Equality of Covid-19 Vaccination Uptake

Public Health Scotland (PHS) produces analysis on the equality of Covid-19 Vaccination uptake. This report updates on a previous analysis, summarised in the State of the Epidemic report published on 11 February 2022.

Since the last publication, PHS have reviewed the processes and methodologies underlying the analysis and concluded that there was an error in the creation of the ethnicity lookup file. This resulted in some bias in the uptake calculations for certain non-White ethnicities, and over-reporting of the estimated uptake in the ethnicity group “White – other”. For more information on the methodology changes, current processes and data sources, please see the PHS Weekly report published on 11 May 2022. Please note that the vaccine uptake rates in this analysis uses different denominators than those in the Vaccine Uptake section, so the figures are not directly comparable.

The updated PHS analysis on the equality of Covid-19 vaccination uptake uses data from 8 December 2020 to 3 May 2022, and contains comparisons by ethnicity and multiple deprivation (based on the SIMD index) in age bands for those aged five and older for dose one, those aged 12 and older for dose two, those aged 16 and older for dose three, and those aged 75 and older for dose four.

In the period 8 December 2020 to 3 May 2022, vaccine uptake for dose one and two was highest among White ethnic groups (88.6% and 84.5% respectively) and lowest among Caribbean or Black ethnic groups (70.0% and 62.1% respectively); similarly, in the period 1 August 2021 to 3 May 2022, dose three vaccine uptake among those aged 16 and older was highest among White ethnic groups (75.4%) and lowest among African ethnic groups (41.7%). The range in uptake of dose 3 was bigger among the older age groups, with 28.4 percentage points difference in uptake between individuals aged 80 and older in White and African ethnic groups. Among the age groups eligible for the fourth dose (those aged 75 and older) uptake was highest among White ethnic groups (68.7%) and lowest in African ethnic groups (37.2%)^[56].

The drop-off refers to the proportion of individuals vaccinated with any dose that do not, for any reason, return for a subsequent vaccination when eligible. For the same time period as above, the drop-off between doses one and two, and between doses two and three, were biggest among African ethnic groups, with 9.0% vaccinated with dose one and not returning for the second (among those aged 12 and older), and 25.8% vaccinated with two doses not returning for the third (among those aged 16 and older). The smallest drop-off was seen among white ethnic groups for these doses (4.1% and 11.3%).

The trends in vaccine uptake over time for the first, second dose (data analysed between 8 December 2020 and 3 May 2022) and third dose (data analysed between 1 August 2021 and 3 May 2022) reflect the JCVI priorities for vaccination. For each age group and dose there is a point at which uptake naturally plateaus as most people who want to get the vaccine when first invited within their priority group, have done so. From that point onwards, this analysis shows that there was a continual decrease in the gap between the ethnic groups for all vaccine doses, indicating that individuals are continuing to come forward for vaccination after their priority group was already invited. For the second dose and third dose, this was particularly seen among African ethnic groups. However, the majority of individuals coming forward for a first and second dose in the past two months have been in the younger age groups.

By multiple deprivation, the uptake of dose one and two among those aged 12 and older was higher among those living in the least deprived areas in Scotland (84.2% and 81.2%), compared to those living in the most deprived areas (75.7% and 69.4%). For both doses, the difference in uptake between the most and least deprived areas increased in the younger age groups. This was also seen among those vaccinated with a third or fourth dose; the third dose had a 76.2% uptake in the least deprived areas and a 56.1% uptake in the most deprived areas (of those aged 16 and older), with the equivalent figures being 71.2% and 61.8% for the fourth dose (of those aged 75 and older).

In the most deprived areas, 6.3% of those aged 12 or older who received their first dose had not received their second, while the equivalent number for the least deprived areas was 3.0%. In the most deprived areas, 15.8% of those aged 12 or older who received their second dose had not received their third, while the equivalent number for the least deprived areas is was 6.2%^[57].

Covid-19 Antibody Estimates

The analysis of antibody prevalence can be used to identify individuals who have had Covid-19 in the past or who have developed antibodies as a result of vaccination. As detailed by the ONS, there is a clear pattern between vaccination and testing positive for Covid-19 antibodies but the detection of antibodies alone is not a precise measure of the immunity protection given by vaccination.

As the pandemic and vaccinations have evolved, the ONS has reviewed how it presents information about antibody levels. To enable enhanced monitoring of antibody levels and waning, in this release, the ONS has introduced an additional antibody series based on a higher level of 800 nanograms per millilitre (ng/mL). This is the highest level at which the ONS can produce a historic back-series of estimates. Please note, it is not based on academic research on protection against Omicron, as sufficient evidence on this is not yet available.

The ONS continues to report the antibody threshold of 179 ng/mL level, but have removed the previously reported standard antibody threshold of 42 ng/mL level from reporting, as all age groups have been at or nearly at 100% antibody positivity at or above 42 ng/mL for some time.

In the week beginning 11 April 2022, the ONS Covid-19 Infection Survey estimated that in Scotland the percentage of adults (aged 16 years and above) living in private residential households in Scotland who are estimated to have antibodies against Covid-19 was 98.9% of adults at or above the 179 ng/mL threshold (95% credible interval: 98.5% to 99.2%), and 94.7% of adults at or above 800 ng/mL (95% credible interval: 93.8% to 95.4%). This suggests that they had the infection in the past or have been vaccinated^[58]. This compares to:

• 98.8% in England (95% credible interval: 98.5% to 99.0%) at the 179 ng/mL threshold, and 95.4% of adults at or above 800 ng/ml (95% credible interval: 94.9% to 95.9%),
• 98.7% in Wales (95% credible interval: 98.2% to 99.0%) at the 179 ng/mL threshold, and 95.6% of adults at or above 800 ng/ml (95% credible interval: 94.8% to 96.4%),
• 99.0% in Northern Ireland (95% credible interval: 98.2% to 99.4%) at the 179 ng/mL threshold, and 94.4% of adults at or above 800 ng/ml (95% credible interval: 91.9% to 96.2%)^[59].

The estimated percentage of the adult (aged 16 years and above) population living in private residential households in Scotland testing positive for antibodies against SARS-CoV-2 at the 179 ng/mL threshold ranged from 97.5% for those aged 80 years and over (95% credible interval: 95.6% to 98.6%) to 99.5% for those aged 70 to 74 years (95% credible interval: 99.1% to 99.7%), in the week beginning 11 April 2022. At the 800 ng/mL threshold, antibody estimates for adults ranged from 89.6% for those aged 80 years and over (95% credible interval: 86.0% to 92.3%) to 96.0% for those aged 16 to 24 years (95% credible interval: 94.2% to 97.2%)^[60].

In the week beginning 11 April 2022, the percentage of children (aged 8 to 15 years) living in private residential households in Scotland who are estimated to have antibodies against SARS-CoV-2 at the 179 ng/mL threshold was: 90.3% for those aged 8 to 11 years (95% credible interval: 82.9% to 94.9%) and 97.2% for those aged 12 to 15 years (95% credible interval: 94.5% to 98.7%)^[61].

Vaccine Effectiveness Against Omicron

The UKHSA reported that vaccine effectiveness against symptomatic disease, hospitalisation, or mortality with the Omicron variant is lower compared to the Delta variant and that it wanes rapidly. High vaccine effectiveness against all outcomes is restored after the booster dose, with effectiveness against symptomatic disease ranging initially from around 60% to 75% and dropping to around 25% to 40% after 15 weeks; however, from 20 or more weeks after the booster dose vaccine, effectiveness against symptomatic disease has almost no effect. Vaccine effectiveness against hospitalisation ranged from 85% to 95% up to six months after the booster dose with little variation between the type of vaccine used for priming or boost. High levels of protection against mortality were also restored after the booster dose, with a vaccine effectiveness of 94% two or more weeks following vaccination, and dropping to around 88% from 10 weeks after the vaccination for those aged 50 and older^[62].

Vaccine effectiveness against symptomatic disease with Omicron BA.2 compared to Omicron BA.1 showed similar results, with BA.1 having an effectiveness of below 20% and BA.2 having an effectiveness of just above 20% after 25 or more weeks following the second dose. The booster dose of vaccine increased effectiveness to around 70% against both BA.1 and BA.2 at two to four weeks following a booster vaccine. Effectiveness dropped to around 50% for BA.1 and BA.2 15 weeks after vaccination. Vaccine effectiveness against hospitalisation ranged from 83% for BA.1 to 87% for BA.2 at 14 to 34 days after the booster dose, and dropped to 73% for BA.1 and 70% for BA.2 after 70 days. These estimates have large overlapping confidence intervals^[63].

More data on vaccine effectiveness against the Omicron variant can be found in the UKHSA vaccine surveillance reports. There is evidence that there is reduced overall risk of hospitalisation for Omicron compared to Delta^{[64] [65]}, with the most recent estimate of the risk of presentation to emergency care or hospital admission with Omicron approximately half of that for Delta^[66]. A recent, non-peer reviewed UK study revealed that risk of Covid-19 related death was 67% lower for Omicron when compared with Delta^[67].