Germany and France are not administering the vaccine to people over 65, citing a lack of data for this population. Meanwhile, South Africa announced on Monday that it would not administer the vaccine over concerns it would not be effective against the B 1.351 variant.
Issuing its interim recommendations for the Oxford University / AstraZeneca COVID-19 vaccine yesterday, the WHO has backed the use of the vaccines in such situations.
People aged 65+
Some countries, such as France and Germany, have limited use of the vaccine to people aged 65 and under. Others, such as the UK, have defended the use of the vaccine in older people.
The WHO notes that the number of participants in trials in this age group was small; but suggests the vaccine is still likely to be effective.
“Because a relatively small number of participants aged 65 years or over were recruited into the clinical trials, there were few cases of COVID-19 in either the vaccine or the control group in this age category, and thus the confidence interval on the efficacy estimate is very wide.
“More precise efficacy estimates for this age group are expected soon, from both ongoing trials and vaccine effectiveness studies in countries that are using this vaccine. Immune responses induced by the vaccine in older persons are well documented and similar to those in other age groups.
“This suggests it is likely that the vaccine will be found to be efficacious in older persons. The trial data indicate that the vaccine is safe for this age group.
The risk of severe disease and death due to COVID-19 increases steeply with age. Older adults are identified as a priority group in the WHO SAGE Prioritization Roadmap. This prioritization is supported by vaccine impact modelling work, even for vaccine efficacy that is substantially below that observed among younger adults administered AZD1222. Taking the totality of available evidence into account, WHO recommends the vaccine for use in persons aged 65 years and older.”
Use against variants
The WHO says the vaccine can be used even if variants are circulating among the local population: although says the emergence of new variants illustrates the need for coordinated surveillance and evaluation of variants.
“Preliminary analyses have shown a slightly reduced vaccine effectiveness of AZD1222 against B184.108.40.206 in the V002 trial in the UK which is associated with only a limited reduction in neutralizing antibody.
“Preliminary analyses from the Phase 1/2a trial (COV005) in South Africa indicate marked reduction in vaccine effectiveness against mild and moderate disease due to B 1.351 based on a small sample size and substantial loss of neutralizing antibody activity. This study was designed to assess efficacy against disease of any severity, but the small sample size did not allow a specific assessment of vaccine efficacy against severe COVID-19. Indirect evidence is compatible with protection against severe COVID-19; however, this remains to be demonstrated in ongoing clinical trials and post-implementation evaluations.
“In view of this, WHO currently recommends the use of AZD1222 vaccine… even if variants are present in a country. Countries should conduct a benefit-risk assessment according to the local epidemiological situation including the extent of circulating virus variants.”
Doses 8 – 12 weeks apart
The WHO says doses of the vaccine should be administered eight to 12 weeks apart.
“According to the manufacturer’s product label, the vaccine can be administered with an interval of 4-12 weeks. In light of the observation that two-dose efficacy and immunogenicity increase with a longer interdose interval, WHO recommends an interval of 8 to 12 weeks between the doses. If the second dose is inadvertently administered less than 4 weeks after the first, the dose does not need to be repeated. If administration of the second dose is inadvertently delayed beyond 12 weeks, it should be given at the earliest possible opportunity. It is recommended that all vaccinated individuals receive two doses.
“There is currently no evidence indicating a need for further doses once an individual has received two doses. The need for, and timing of, additional doses will be evaluated as further data accumulate.”
Children and pregnant women
As with other vaccines, the WHO does not recommend the use of the vaccine with pregnant women or children given a lack of trial data for these populations. The vaccine is recommended for use in people aged 18+.