New studies explore waning immunity and vaccine efficacy against long COVID

Two new studies on COVID-19 vaccines have emerged from the United Kingdom. One deals with general efficacy and another is on vaccine effectiveness in preventing or reducing the chances of long COVID-19.

The findings revealed two shots of the Pfizer, Inc vaccine provided high levels of protection for a short period of time — six months — while infection preceded by double vaccination resulted in high levels of immunity that lasted longer than a year.

This study was backed by the UK Health Security Agency (UKHSA) and published in the New England Journal of Medicine (NEJM) on February 16.

The second study, conducted by UKHSA, looked at vaccination before and after infection and the change in protection provided against long COVID.

A total of 15 studies were examined. Seven looked at whether vaccination before infection reduced symptoms or incidence of long COVID.

Another seven looked at people who got vaccinated after being infected and its impact on symptom and incidence of long COVID, while one study examined both scenarios.

Six of the eight studies which looked at the effectiveness of vaccination before infection “suggested that vaccinated cases (one or two doses) were less likely to develop symptoms of long COVID following infection, in the short term (four weeks after infection), medium term (12 to 20 weeks after infection) and long term (six months after infection),” the study noted.

Symptoms such as fatigue, headache, weakness in arms and legs, persistent muscle pain, hair loss, dizziness, shortness of breath, anosmia, interstitial lung disease, myalgia and other pain were less prevalent in the medium or long term among fully vaccinated cases.

On vaccination in people previously infected with the virus and suffering from long COVID, three studies found that “more cases reported an improvement in symptoms after vaccination, either immediately or over several weeks.”

Three more studies compared those who were suffering from long COVID and got vaccinated soon after while another group that remained unvaccinated.

The findings revealed that “people with long-COVID were less likely to report long COVID symptoms shortly after vaccination and over longer periods, than people with long COVID who were not subsequently vaccinated.”

However, there were some cases in every such study where symptoms worsened after vaccination.

Of the 15 studies examined, four each were conducted in the United Kingdom and United States, two in India, one each in France, Israel and Indonesia while the remaining two studies had participants from across the world.

While the definition of long COVID differed from one study to another, it broadly considered patients whose symptoms persisted for more than “four weeks after initial infection.”

While this study addresses issues of long COVID, the NEJM study explored the general efficacy of COVID-19 vaccines and how much it wanes over time — a pressing concern with the emergence of omicron and its immunity evading characteristics.

Of the 35,768 participants examined between December 7, 2020 and September 21, 2021, 27 per cent were infected with the virus before being vaccinated.

With 97 per cent of participants being fully vaccinated, with either the Pfizer or AstraZeneca shot, vaccine coverage was high.

Those who received two shots of the Pfizer vaccine with long intervals between doses recorded high levels of protection — between 72 per cent and 92 per cent — for two months.

It reduced to between 22 per cent and 69 per cent, six months after the second dose.

“We found no significant differences in the risk of infection when the BNT162b2 vaccine was administered with a short or long interval between doses, although we found considerably lower protection after two doses of the ChAdOx1 nCoV-19 vaccine (AstraZeneca) than after two doses of the BNT162b2 vaccine (Pfizer),” the study noted, adding that the delta variant also emerged at a time when immunity had begun waning.

Immunity of those who were infected but did not get vaccinated began waning after a year. “Vaccination after previous infection appeared to boost and extend immunity and we found no indication of waning of this immunity even more than one year after primary infection,” the study noted.

It further argued that protection provided by primary vaccination followed by a booster shot was similar to infection followed by primary vaccination.

These findings strengthen the case for vaccines. However, inequity continues to persist. According to website Our World in Data, Africa has fully vaccinated just 12 per cent of its population.

In comparison, Australia has fully vaccinated 79 per cent of its total population, South America has done 69 per cent, Europe has done 64 per cent, Asia is at 63 per cent while North America has done 61 per cent.

“No other event like the COVID-19 pandemic has shown that reliance on a few companies to supply global public goods is limiting and dangerous. In the mid- to long-term, the best way to address health emergencies and reach universal health coverage is to significantly increase the capacity of all regions to manufacture the health products they need, with equitable access as their primary endpoint,” World Health Organization Director-General, Tedros Adhanom Ghebreyesus said at a media briefing February 18.

In this regard, Egypt, Kenya, Nigeria, Senegal, South Africa and Tunisia were selected as the first six recipients to receive the technology needed to produce mRNA vaccines.

This is part of the global mRNA technology transfer hub which was established in 2021 to address manufacturing gaps in low and middle-income countries.

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