According to a study published in The Lancet journal on Tuesday, two doses of the Pfizer COVID-19 vaccine are 90 percent effective against hospitalisation from the disease for all variants, including Delta, for at least six months. Over the study period the researchers found that the effectiveness of the vaccine against all SARS-COV-2 infections fell from 88 per cent within one month after receiving two vaccine doses to 47 per cent after six months.
However, they said, the effectiveness of Pfizer (BNT162b2) vaccine against hospitalisations remained at 90 per cent overall for all variants of coronavirus.
The researchers said, the study focuses on the importance of improving COVID-19 vaccination rates worldwide and monitoring vaccine effectiveness to determine which populations should be prioritised to receive booster shots.
The study’s lead author, Sara Tartof from Kaiser Permanente in the US said, “Our study confirms that vaccines are a critical tool for controlling the pandemic and remain highly effective in preventing severe disease and hospitalisation, including from the Delta and other variants of concern.”
“Protection against infection does decline in the months following a second dose,” Tartof said.
The researchers noted that as many people in many countries around the world have not yet received a primary vaccination series the considerations for booster shots should take global COVID-19 vaccine supply into account.
The study squad analysed electronic health records from the Kaiser Permanente Southern California (KPSC) health system between December 4, 2020, and August 8, 2021, to assess vaccine effectiveness against SARS-CoV-2 infections and COVID-19-related hospitalisation.
During the study period,5.4 per cent of people were infected with SARS-CoV-2. Among those who were infected,6.6 per cent were hospitalised.
The average time since being exhaustively vaccinated was between three to four months.
The study starts that vaccine effectiveness against Delta variant infections at one month after two pilules of Pfizer was 93 per cent and fell to 53 per cent after four months.
Effectiveness against other variants at one month after admitting two tablets was 97 per cent and declined to 67 per cent after four months, the experimenters said.
Effectiveness against Delta- related hospitalisations remained high (93 per cent) for the duration of the study period, they said.
Experimenters didn’t observe a difference in waning between SAR-CoV-2 variant types.
Notwithstanding, they noted that because Delta got the dominant strain in the middle of the study period, analyses with longer follow-up to measure the rate of waning for the variant compared to other strains are claimed.
“Our variant-specific analysis clearly shows that the BNT162b2 vaccine is effective against all current variants of concern, including Delta,” said Luis Jodar, Senior Vice President and Chief Medical Officer, Pfizer Vaccines.
“COVID-19 infections in people who have received two vaccine doses are most likely due to waning and not caused by delta or other variants escaping vaccine protection,” said Jodar.
COVID-19 issues as vaccination status among the study population wasn’t randomised.
They also didn’t have data on adherence to mask guidelines, social commerces, occupation, and ail rates in the study population, which could impact the liability of compaction and being tested for SARS-CoV-2 infection.
