Omicron has brought shorter, more intense waves of infections across the UK, with the ZOE Covid study app measuring a peak of around 350,000 cases a day earlier this month, before cases nearly halved over the next two weeks. However, rather than bringing a prolonged period of immunity to the population, scientists warn the ability of the BA.4 and BA.5 sub-variants to evade resistance built up from previous infections means people could see themselves getting infected again Covid in just a few weeks. Official UK government figures have fallen significantly since the end of free mass Covid tests in April, but the data still shows a narrower gap between the peak of each respective Covid wave since March 2020. After the Alpha variant peaked at 352,000 weekly infections in January 2021, it took more than six months for the Delta wave to peak at 303,000 cases per week last July. However, since the first Omicron wave saw official government figures reach an all-time high of more than 1 million cases per week at the end of December 2021, there have been three consecutive Omicron peaks in just seven months. It is a trend that has already been recognized in countries such as Australia and New Zealand and in some US states. In Australia, health experts are increasingly concerned about Covid re-infections and recently recommended that official guidelines on the period of immunity after infection be reduced from 12 weeks to just 28 days, meaning people should be tested and self-isolate if they have symptoms more than four weeks later. is recovering. Western Australia’s chief health officer, Andy Robertson, said: “BA.4 and BA.5 make up a growing proportion of our cases, rising to more than 60 per cent of cases in the last week. “This means that people who have had Covid-19 should be retested and isolated if they have symptoms more than 28 days after recovering from Covid-19.” The high levels of re-infection are partly a product of Omicron, which has the ability to evade immunity unlike previous variants of Covid-19, and experts believe the UK is now seeing similar trends. Professor Azeem Majeed, head of primary care and public health at Imperial College London, told i: “We have seen a narrowing of the gaps between waves of Covid-19 in the UK since the introduction of Omicron and its sub-variants. “Omicron appears to have a greater ability to evade immunity from vaccination and previous infection. This leads to more people getting reinfections and sometimes a very short gap between infections.” The small gap has also meant that newer sub-variants of Omicron are quickly replacing older ones. The original Omicron variant, BA. 1, lasted about a month and a half before being overtaken by the second Omicron variant, BA. 2 in the UK which has now been superseded by a new variant, BA. 5. In contrast, Delta was the dominant variant in England for over 200 days. A vaccine that better targets the Omicron variant may better provide protection against the variant and its sub-variants. Earlier this week Pfizer announced that it had started a mid-stage study of a modified Covid-19 vaccine targeting both the original and the BA 2 Omicron subvariant. In July, the Food and Drug Administration recommended that both Pfizer and Moderna move forward with developing vaccine boosters specifically for Omicron. The FDA noted that these shots will hopefully be ready for use by mid-fall. It is currently unknown whether the UK will offer an updated vaccine for the Autumn booster programme. As Covid has developed, the age distribution of cases has also changed significantly, with people over 60 now accounting for the largest share of Covid-19 infections in England for the first time since the initial variant in early 2020. While the first Omicron variant, BA. 1, was largely seen in people under 19, this has now changed significantly with people under 19 now accounting for the smallest share of new infections compared to other age groups. Outbreaks of Omicron’s BA 2 and BA 5 subvariants represent the first time that people under 19 accounted for the smallest share of infections. During every other variant of Covid except the beginning of the original strain, the young have dominated the spread of the disease. In part, the waves of Covid are also getting shorter because, despite Omicron’s ability to wipe out immunity, immunity continues to rise in the UK through both infection and vaccination. This means that the new variants are suppressed in a way that the previous ones were not. Professor Beate Kampmann, Professor of Pediatric Infections & Immunity. and Director of the Vaccine Centre, London School of Hygiene and Tropical Medicine, told i: “Immunity to SARS-Cov2 is increasing in the population due to both prior infection and vaccination. “Therefore, infections with new variants will be at least partly suppressed by community and individual immunity, and waves of new variants will not last as long unless there is a very substantial change in the composition of the virus. We don’t see this level of immune escape.” However, as Professor Kampmann notes, it is not a given that Covid waves will become less severe and this depends on the assumption that immunity remains strong, which is based on the fact that there are no substantial changes in the composition of the virus. So far that’s been the case, and there’s certainly reason to hope that with a round of autumn amps targeting Omicron that trend will continue, although that’s by no means guaranteed.
